Svitolina has endured a disappointing start to the season and there was no upturn in fortunes in Doha, where she was beaten 6-3 6-3 in the second round.
Martic got past Barbora Strycova in the first round in Dubai last week, but the Czech gained revenge with a 4-6 6-1 6-1 victory to move into round two.
Alison Riske, the 13th seed, lost an all-American encounter with Jennifer Brady, while 17th seed Donna Vekic went down in straight sets to Iga Swiatek.
Kiki Bertens had no such trouble, winning 6-2 6-4 against Karolina Muchova to reach the third round, while Elena Rybakina came from a set down to oust Sorana Cirstea.
TEENAGER ANISIMOVA STARTLES SVITOLINA
Svitolina has won just four matches this year and it was 18-year-old Anisimova who inflicted another blow on the world number seven.
The American teenager claimed a first top 10 win of 2020, taking just 64 minutes to sail through in her first appearance in this tournament.
She struck 27 winners and saved all three break points faced and will take on either Swiatek or Svetlana Kuznetsova for a place in the quarter-finals.
RYBAKINA ROARS BACK
Rybakina suffered the agony of a defeat to Simona Halep in the final of the Dubai Tennis Championships on Saturday.
The 20-year-old rising star from Kazakhstan, up to a career-high 17th in the rankings, gave another demonstration of her fighting spirit by roaring back to beat Cirstea 3-6 6-3 6-1.
Rybakina already has 20 victories to her name this season and will be expected to make it 21 when she takes on Alison Van Uytvanck in the second round.
SUAREZ NAVARRO SETS UP BATTLE OF FORMER CHAMPIONS
Carla Suarez Navarro coasted to a 7-5 6-0 first-round victory over Zhang Shuai on day two of the tournament.
The Spaniard's reward will be a tough encounter with Petra Kvitova, two players who have experienced glory in Doha.
Suarez Navarro won the tournament in four years ago and Kvitova was crowned champion in 2018.
Playing her first match since losing to Elena Rybakina in the semi-finals of the Australian Open, Azarenka dispatched outsider Oz 6-1 6-1.
Azarenka, a two-time champion in Doha, only needed an hour and seven minutes to book a meeting with Belinda Bencic or Viktoriya Tomova.
The Belarusian broke twice in the first set and four times in the second, failing to hold just the once in a commanding display.
Eighth seed Veronika Kudermetova battled her way past Barbora Krejcikova, winning 6-4 3-6 7-6 (7-5).
Karolina Muchov secured an impressive 6-2 6-2 win over Martina Trevisan in the opening first-round match of the day.
In her first match since the Australian Open, world number one Barty triumphed 6-3 6-2 in her opening match at the WTA Premier event.
Australian Open champion Sofia Kenin endured another difficult day, though, losing to 19-year-old Dayana Yastremska, while defending champion Elise Mertens also bowed out.
Karolina Pliskova, Belinda Bencic and Petra Kvitova all advanced, while Melbourne runner-up Garbine Muguruza was in imperious form as she dispatched Ajla Tomljanovic for the loss of just three games.
There were also wins for Saisai Zheng over Vera Zvonareva, Ons Jabeur against Jennifer Brady, Maria Sakkari over Tereza Martincova and Svetlana Kuznetsova against Iga Swiatek.
BARTY BLASTS OUT OF THE BLOCKS
Playing for the first time since losing to Kenin in the Australian Open semi-finals, Barty produced a disciplined performance to beat Siegemund in 73 minutes.
Barty hit 19 winners to 16 unforced errors but admitted she lost focus at some key moments.
"Happy overall to be able to switch on when I really needed to. Disappointing to have a few lapses in concentration but also a credit to my opponent, she came up with some really good stuff in runs to be able to break me a few times," she said.
Barty will face Elena Rybakina next after she battled to beat Alison Van Uytvanck 5-7 6-2 7-6 (10-8).
KENIN WOES CONTINUE
Kenin has now lost three times since lifting the first grand slam singles title of the season, the American slumping to a 6-3 7-6 (7-4) loss to Yastremska.
"It's really frustrating," she said. "Obviously coming off of Melbourne where I felt I was playing the best tennis of my life coming down to playing, not the worst tennis, but not playing the tennis I want to be playing."
Yastremska will now meet Muguruza, who wasted little time in beating Tomljanovic 6-1 6-2.
PLISKOVA CHARGES ON AS SEEDS PROGRESS
Pliskova was beaten in the quarter-finals in Dubai by Rybakina but looks determined to go the distance in Doha, producing an accomplished performance to oust Bernarda Pera 6-3 6-0.
Fourth seed Bencic was given a tougher time by Veronika Kudermetova before claiming a 6-4 4-6 7-6 (7-4) win that took more than two and a half hours.
Aryna Sabalenka edged a tight encounter with Anett Kontaveit 7-5 2-6 7-5, while Kvitova ended the challenge of Carla Suarez Navarro 4-6 6-3 6-0.
Defending champion Mertens is out, though, falling to Yulia Putintseva 4-6 6-3 6-2.
World number one Barty needed three sets to see off Australian Open finalist Muguruza in Doha, while Kvitova won a pair of tie-breaks in her quarter-final with Jabeur.
Veteran Svetlana Kuznetsova earned a share of tournament history with an upset win over fourth seed Belinda Bencic.
The Russian now faces Aryna Sabalenka, who came from behind to defeat Saisai Zheng in the day's opening match.
BARTY OUT TO CONTINUE KVITOVA RUN
Barty endured a second-set dip in her 6-1 6-7 (4-7) 6-2 beating of Muguruza, who has reached at least the last eight in each of her five tournaments in 2020.
The Australian, playing at her first event since reaching the semis of her home slam in Melbourne, did not face a single break point in the opening set but was met with a much sterner test in the second.
Barty raced into a 5-2 lead in the decider, though, and fought back from 40-15 in the final game to set up a showdown with Kvitova, who she has beaten in their previous four meetings - including a straight-sets win at the Australian Open.
Kvitova, the 2018 champion, edged to a 7-6 (7-2) 7-6 (7-4) win over Jabeur, who has enjoyed a stellar year thus far and became the first Arab woman to reach a major quarter-final in Melbourne.
MILESTONE FOR KUZNETSOVA
Kuznetsova was in devastating form against Bencic, hitting 39 winners and just 15 unforced errors in a 6-4 6-4 triumph.
A runner-up in 2004 and 2007, Kuznetsova now has 19 match wins in Doha, which ties the record held by retired former world number one Caroline Wozniacki.
"I have amazing memories," said Kuznetsova, who is in to her first Doha semi since 2007.
"It was my first time when I beat Justine [Henin] here [in the 2004 semi-finals] and it was like I was a kid, I was 19.
"I climbed from number 30-something to number 13 or number 14 and it was amazing. It was so long ago it was like another life, but it really happened to me - I didn't watch it in the movies."
Sabalenka will try to end Kuznetsova's run after a 3-6 7-6 (7-2) 6-3 defeat of Zheng.
The seventh seed triumphed at the Abu Dhabi Open last week to add to her Adelaide International 2 success from January and is now seeking another title in Doha.
Bencic eased to a 6-0 6-1 win against Bulgarian qualifier Tomova and will face two-time tournament winner Victoria Azarenka for a place in the quarter-finals.
Maria Sakkari also advanced on Tuesday, overcoming Zheng Qinwen 6-2 3-6 6-3, as did fellow seeded player Daria Kasatkina with a 7-6 (7-5) 6-2 win against Rebecca Marino.
Zheng may have suffered an early exit, but last season's WTA Newcomer of the Year produced the shot of the tournament with a winning tweener en route to taking the second set.
Petra Kvitova, another two-time winner in Qatar, defeated Zhang Shuai 7-5 6-2, while Danielle Collins beat Elise Mertens 6-4 7-6 (8-6) and will now face top seed Iga Swiatek.
Second seed Jessica Pegula will take on Jelena Ostapenko, meanwhile, after the Latvian proved too strong for Madison Keys in a 7-5 6-2 victory.
Kvitova needed little over an hour to get past 16th-ranked Muguruza 6-2 6-1, securing her 28th victory on the WTA Tour and first since winning in Stuttgart in 2019.
The Czech was the Qatar Open runner-up last year to Aryna Sabalenka and champion over Muguruza in 2018, while she did not compete in 2019.
"It's been a great run in Doha," Kvitova said on court post-match.
"It's been a great whole week. I just feel like home a little bit. I love the court, I love everything and the people are really friendly as well."
Two-time Wimbledon champion Kvitova hit 11 winners and was dominant on her serve throughout.
After a strong opening set, Kvitova was broken by Muguruza early in the second but the Czech hit back by winning the next six games to secure the win, extending her head-to-head record over the Spaniard to 5-1.
Muguruza said: "Today I think Petra played very well from the baseline, and it was hard to try to make her move, or try to do much… It really wasn't my day."
Former world number one Halep, champion in Qatar back in 2014, was off the pace as Caroline Garcia claimed just her second win in nine meetings against the Romanian with a 6-4 6-3 triumph.
Number 10 seed Svitolina also suffered an early exit after ending up on the wrong side of an almost three-hour slog, with Tereza Martincova eventually succeeding 6-7 (2-7) 7-5 7-6 (7-5).
But fifth favourite Muguruza – a two-time finalist, including in 2021 – did not have much as trouble as she outfought Sorana Cirstea 7-6 (7-4) 6-1 in a second-round contest, with Kontaveit coasting through to round three in similar fashion with a 6-2 6-3 win over Ana Konjuh.
Jelena Ostapenko, who is a former finalist in Doha and champion in Dubai last week, managed a sixth consecutive victory in the Middle East as she downed Oceane Dodin 6-4 6-2 to reach the second round, while 11th seed Elena Rybakina fell at the first hurdle to Jacques Cristian in a 6-4 6-3 loss.
Angelique Kerber, the 13th ranked player at the tournament, was another surprise first-round loser as she fell 4-6 6-3 6-2 to Jil Teichmann.
Cori Gauff secured her spot in the second round with a straightforward 6-2 6-3 victory over American compatriot Shelby Rogers, while 16th seed Elise Mertens battled to a 6-3 2-6 7-5 win over Jasmine Paolini.
Meanwhile, defending champion Petra Kvitova had no trouble easing past Irina-Camelia Begu 6-3 6-1, and Daria Kasatkina edged out Ajla Tomljanovic 6-4 6-7 (4-7) 6-2.
The Tunisian has surged to a career-high ranking of 44 having made history by reaching the quarter-finals of the Australian Open in January.
What it is rapidly developing into a breakthrough year saw another high point on Wednesday as she emerged victorious from a gruelling three-set battle with third seed Pliskova.
Kiki Bertens was another to suffer a surprise loss as Zheng Saisai came from a set down to see off the seventh seed.
Belinda Bencic, Petra Kvitova and Aryna Sabalenka all progressed, while world number one Ashleigh Barty was one of two players to receive a walkover into the quarter-finals, where she will meet Garbine Muguruza.
JABEUR MAKES MORE HISTORY
It has already been an impressive year for Jabeur.
She added another achievement to an increasingly impressive CV by progressing to the last eight in Doha.
Having lost to Simona Halep in a third-set tie-break in Dubai, Jabeur made sure to finish the job against Pliskova, hitting 33 winners to prevail 6-4 3-6 6-3 in a thriller and knock out the 2017 champion.
ZHENG BATTLES BACK
Few would have predicted Bertens succumbing to Zheng considering she dropped just one set en route to the St. Petersburg Open title earlier this month.
There appeared little sign of a shock when Bertens took the first set, but Zheng superbly battled back to claim a 3-6 6-3 6-4 win after two hours and 10 minutes.
Eighth seed Kvitova came through a frenetic contest with Jelena Ostapenko 6-2 5-7 6-1, while Bencic and Sabalenka earned straight-sets victories over Yulia Putintseva and Maria Sakkari.
MUGURUZA SETS UP BARTY CLASH
Though she was unable to overcome Sofia Kenin in the Australian Open final, Muguruza has been a player revitalised in 2020.
A clash with rising star Dayana Yastremska presented a significant hurdle, but she cleared it in relatively routine fashion.
Despite hitting only two winners, Muguruza capitalised on 29 unforced errors from Yastremska as the two-time grand slam champion wrapped up a 6-2 6-4 success.
Barty, whose meeting with Elena Rybakina was cancelled after the Kazakh withdrew with an abductor strain, is next for Muguruza. Svetlana Kuznetsova, meanwhile, progressed as Amanda Anisimova pulled out because of illness.
Champion in St Petersburg two weeks ago, Kontaveit extended her winning run to eight matches following a 6-4 6-1 success.
The opening set was neck and neck until Kontaveit won 15 out of 16 points from 30-30 at 4-4 to draw first blood and establish a 2-0 lead in the second.
The Estonian, who registered just 12 unforced errors throughout the contest, then took 12 of the last 15 points to advance to the last four.
"At times, it was just kind of fun because I felt like the level was really good, and I was playing really well," said Kontaveit, who has won nine of her last 13 matches against top-10 opposition.
"I think I have this confidence that I can go deep every week that I'm playing, and I'm not setting these mental barriers to myself that I used to do.
"I'm very happy with being in the semi-finals, but I also feel like I can still go deeper, I can still do more. So, I'm not too satisfied yet with this result. I feel like if I play well or if I'm consistent, I have a chance with anyone.
"I'm really happy that I'm bringing a good level of tennis consistently every tournament. I think that's something that I'm just most pleased with."
In the semi-finals, Kontaveit will face another in-form player in Jelena Ostapenko, who saw off Garbine Muguruza in straight sets.
Having triumphed in Dubai last week, the 15th seed has now recorded nine successive victories for the first time in her career after prevailing 6-2 6-2.
Ostapenko struck 39 winners and claimed 15 of 18 points on her opponent's second serve as she moved a step closer to a maiden title in Doha, having reached the final six years ago.
Meanwhile, Iga Swiatek is through to her first WTA 1000 semi-final on a hard court after a 6-2 6-3 win over Aryna Sabalenka.
The former French Open champion won seven out of eight breakpoints, while reeling off six successive games in the second set to secure a comfortable victory.
Next up for her is Maria Sakkari, who recorded her third win against Coco Gauff in four meetings after prevailing 6-3 6-3.
The sixth seed is through to her sixth semi-final at WTA 1000 level or above – and targeting her first such title.
Swiatek advanced to the Doha showpiece for the first time after managing her first win over Sakkari in four attempts with a 6-4 6-3 triumph on Friday.
The Pole was in imperious form as she delivered 20 winners to overcome sixth seed Sakkari in an hour and 28 minutes, collecting her seventh top-10 win and second straight such win after defeating Aryna Sabalenka in the quarter-finals.
The seventh seed will now meet Kontaveit, who continued her impressive streak with a 6-1 6-4 win over Ostapenko in just 68 minutes.
Ostapenko headed into the clash on a career-best nine-match winning run, but succumbed to her fourth loss in five meetings with the fourth seed in Qatar.
Ostapenko did have back-to-back break points at 5-5 in the final set, but Kontaveit managed to hold on for victory.
"She can outplay anyone, and then she might not find the consistency sometimes, so you have to be ready for that," Kontaveit said of Ostapenko.
"I was trying to play a consistent match and just do my best on my serve and hold on to it, especially in the second set when I was a break up.
"Sometimes when she's on fire, her returns are unplayable and it's just very difficult.
"But I kept repeating to myself, 'I'm really good at serving it out, I'm really good at serving it out,' and eventually managed to do that.
"How you approach the match, how you're approaching the service games, I think if you're trying to be aggressive [...] that has a lot of effect on the serve."
It will be the seventh final that Kontaveit has contested since last August, converting those appearances into five titles so far. Kontaveit and Swiatek share a pair of wins apiece in previous clashes.
World number one Swiatek was already assured of her semi-final place heading into Thursday as Belinda Bencic's withdrawal had granted her a walkover.
She could watch on then as Kudermetova upset fourth seed Gauff 6-3 3-6 6-1 in Doha.
Swiatek has won each of her previous two matches against Kudermetova in straight sets, but the world number 11 will be on a high after her first top-10 win of the season.
It will be the 25-year-old's second semi of the season, although she withdrew from her Adelaide 2 match-up against Bencic.
While Gauff is out, there remains American representation as her doubles partner Jessica Pegula made light work of Beatriz Haddad Maia 6-3 6-2.
Pegula, the second seed, will face Greece's Maria Sakkari, who overcame third favourite Carolina Garcia 6-2 6-7 (5-7) 7-6 (7-5) in a battling encounter.
Kvitova saw off Pegula in straight sets, triumphing 6-4 6-4, meaning she will be involved in the final of the tournament for a third time in four years.
Having twice let slip breaks in the opener, the 2020 runner up edged ahead again at 5-4 before serving out for a 1-0 lead.
Pegula appeared set to draw level when she raced 3-0 ahead in the next, only to be pegged back by Kvitova, who hit 26 winners and the same number of unforced errors. Victory was eventually sealed after one hour and 18 minutes on court.
The two-time Wimbledon champion secured the trophy in Doha three years ago by beating Muguruza, who did not even have to hit a ball to progress on Friday after opponent Victoria Azarenka withdrew from their semi-final due to a back injury.
That title showdown in 2018 went the distance, Kvitova rallying after losing the opening set to eventually prevail.
"I think it's going to be a tough match," Muguruza said, according to the WTA Tour's official website.
"We played here in another final three years ago, so just looking forward to playing that match and hopefully getting the trophy."
The Spaniard has been in impressive form this week, ending Aryna Sabalenka's hopes of defending her crown in the last 16 before thrashing Maria Sakkari in a lopsided quarter-final.
Meanwhile, in Friday's action at the Lyon Open, second seed Fiona Ferro rallied from a set down to beat fellow Frenchwoman Clara Burel and reach the semi-finals.
Ferro's 2-6 6-1 6-3 triumph means she is certain to break into the top 40 in the world for the first time in her career.
The only other seed left in the draw is Paula Badosa, the Spaniard knocking out Kristina Mladenovic. Her reward is a last-four clash with qualifier Clara Tauson, conqueror of Camila Giorgi in straight sets.
World number one Barty had survived a three-set clash with Garbine Muguruza to reach the last four in Doha, but two-time Wimbledon champion Kvitova proved too strong on Friday.
Barty appeared to have the momentum after levelling the match by taking the second set in comfortable fashion.
However, an engrossing third went the way of Kvitova, even if was far from straightforward.
A sliced Barty backhand into the net gave Kvitova a break in the fifth game of the decider, only for the Czech to surrender it straight back when she fired wide off the same wing.
Yet a blistering crosscourt backhand return earned Kvitova the advantage again and a place in the final was secured when Barty looped a forehand wide to seal a 6-4 2-6 6-4 win for the 2018 champion.
Sabalenka's victory over Svetlana Kuznetsova was more routine.
The 21-year-old is making her debut at the tournament, but youth triumphed over experience in comfortable fashion as she needed only an hour and 17 minutes to prevail 6-4 6-3.
It is now 10 career WTA singles finals for Sabalenka, who has lost two of her three meetings with Kvitova, her solitary win coming at the 2018 US Open.
Two-time Wimbledon champion Kvitova lost to Aryna Sabalenka in the 2020 final but has looked on top form throughout the week in Doha.
Kontaveit proved a tough opponent for the fourth seed, however, and Kvitova – the 2018 champion – needed three sets to progress 6-3 3-6 6-2.
"I'm really glad that after losing the second set, which I probably didn't play the best, I started very well in the third," said Kvitova.
"I learned that the return was pretty good from my side. I was going for it – first point, first shot – and I think that made a big difference. In the rally, it was 50-50 and anybody could win it, but when I put the pressure from my return, it was really very nice."
Her reward is a semi-final tie with qualifier Jessica Pegula, who caused an upset by defeating second seed Karolina Pliskova 6-3 6-1.
Pegula reached the Australian Open quarter-finals last month and played with supreme confidence to oust the 2017 champion and reach her maiden semi-final at a WTA 500 event.
The other half of the draw will see Victoria Azarenka taking on Garbine Muguruza.
Azarenka triumphed 6-2 6-4 over top seed Elina Svitolina, with the two-time Doha champion maintaining her unbeaten record against the Ukrainian to reach the 60th WTA semi-final of her career.
Muguruza, meanwhile, battled past Maria Sakkari 6-3 6-1 to complete the last four.
At the Lyon Open, French duo Kristina Mladenovic and Clara Burel booked their places in the last eight, beating Margarita Gasparyan and Aliaksandra Sasnovich respectively.
Spaniard Paula Badosa awaits Mladenovic, while teenage wildcard Burel takes on compatriot and second seed Fiona Ferro in what is her first WTA quarter-final.
There were also victories for Greet Minnen and Viktorija Golubic.
The Belgian, seeded 16th in Doha, produced a dominant display to triumph 6-1 6-2 and set up a meeting with either Anastasia Pavlyuchenkova or Yulia Putintseva.
Australian Open runner-up Garbine Muguruza endured a much tougher outing at the WTA Premier 5 event than Mertens, requiring three sets to see off Daria Kasatkina.
The two-time grand slam champion prevailed 7-5 5-7 6-3 after two hours and 49 minutes, with Ajla Tomljanovic up next for the Spaniard.
Jelena Ostapenko, who won the French Open in 2017, was pushed all the way in a 7-5 2-6 7-5 victory over Jil Teichmann, while top seed Ash Barty learned that she will face Laura Siegemund following the German's defeat of Yaroslava Shvedova.
Elsewhere in the draw, Veronika Kudermetova dumped out Kristina Mladenovic despite losing the second set 6-0, Svetlana Kuznetsova ousted Cagla Buyukakcay, and Karolina Muchova was too strong for Magda Linette.
Tomljanovic beat fellow Australian Priscilla Hon, and there were also wins for Bernarda Pera, Alison Van Uytvanck, Amanda Anisimova and Ons Jabeur.
Muguruza prevailed in a high-quality contest that required a third set to decide the outcome, the world number 16 and two-time grand slam champion eventually triumphing 6-2 6-7 (7-5) 6-3 after two hours, 18 minutes on court.
Sabalenka had won their only previous meeting but the third seed saw her hopes of retaining the trophy dashed, not helped by only managing to convert four of the 13 break-point opportunities she created in the match.
Muguruza – who matched 41 winners with the same number of unforced errors – finished in fine style, claiming the final four games in a row to set up a meeting with Maria Sakkari, who defeated Madison Keys in straight sets.
"I'm very motivated to play top players," Muguruza said in her post-match press conference, according to the WTA Tour's website. "Like everybody, I worked hard. I'm fighting for trophies, to play well in big tournaments, in good tournaments.
"Today I was facing a top player, and I knew I have to go out there with a big, fighting spirit, and be strong to be able to win against these tough opponents."
While the 2020 winner is no longer involved, former champions Victoria Azarenka and Petra Kvitova both made it beyond the second round with straight-sets wins in Wednesday's action.
Azarenka, who claimed the title in 2012 and then returned to successfully retain it a year later, saw off qualifier Laura Siegemund 6-4 6-2.
Kvitova, meanwhile, eased past Anastasia Pavlyuchenkova. The fourth seed went all the way in 2018 and is now into the last eight this year – a 6-1 6-3 result paving the way for a clash with Anett Kontaveit.
Top seed Elina Svitolina is also through – and will face Azarenka next – after needing little over an hour to defeat Misaki Doi 6-1 6-2.
Karolina Pliskova, the second seed, found life far tougher against Ons Jabeur however, eventually coming out on top 6-4 4-6 7-5 in a thriller.
Meanwhile, at the Lyon Open, second seed Fiona Ferro progressed to the last eight on home soil after opponent Tereza Martincova was forced to retire when 4-1 down in the second set, having already lost the opener too.
Alize Cornet is another French favourite hoping to make home advantage tell in the tournament; the fifth seed rallied from a set down to beat compatriot Clara Burel 1-6 6-1 6-3.
Jabeur reached the finals of Wimbledon and the US Open last season but was unable to build on that strong finish to 2022 at the start of this year.
The Tunisian exited the Australian Open in the second round, having complained of a knee injury.
Jabeur said after her defeat to Marketa Vondrousova she would need "time to recover and get healthier", and she has not been seen on the WTA Tour since.
The Qatar Open was due to see Jabeur's return next week, but an Instagram post has now confirmed she will miss both that tournament and the subsequent Dubai Tennis Championships.
"In order to take care of my health situation, my medical team have decided that I need to get a minor surgery in order to be back on the courts and perform well," she wrote.
"I will have to retire from Doha and Dubai, and this is breaking my heart.
"I would like to say sorry to all the fans out there in the Middle East that waited for this reunion.
"I promise I will come back to you stronger and healthy."
Playing for the first time since she was knocked out of the Australian Open by Elena Rybakina in the fourth round last month, normal service was resumed by the domineering world number one in Doha.
The top seed brushed Collins aside in only 53 minutes, racing to a 6-0 6-1 victory to march into the third round.
Collins only won four points as she suffered the misery of a first-set bagel, an inspired Swiatek taking the opener in only 21 minutes.
Swiatek's run of games won was ended at nine when Collins got on the board at 3-1, but the Pole broke for a fifth time before serving it out for an emphatic victory.
The 21-year-old three-time grand slam champion, who made only six unforced errors, will do battle with Belinda Bencic for a place in the quarter-finals.
Bencic beat two-time champion Victoria Azarenka 1-6 7-6 (7-4) 6-4 to take her place in the last 16, storming back from 4-1 down in the second set when she appeared to be on her way out.
Second seed Jessica Pegula saved two match puts as she dug deep to beat Jelena Ostapenko 6-2 2-6 7-5 to set up a meeting with Beatriz Haddad Maia, who beat Daria Kasatkina in straight sets.
Fourth seed Coco Gauff got the better of Petra Kvitova 6-3 7-6 (8-6), while Veronika Kudermetova and Maria Sakkari also made it through.
Kvitova won the tournament in 2018 and had beaten world number one Ash Barty in the last four, yet she was unable to secure the victory that would have moved her back into the world's top 10.
Sabalenka's powerful serving and brutal groundstrokes were the difference, while she saved all five break points she faced in one game during the second set.
The triumph, Sabalenka's second successive Premier 5 title after her victory at the WTA Elite Trophy in September, ensured the 21-year-old will move to 11 in the world rankings, ahead of Kvitova at 12.
Sabalenka had two break points in Kvitova's opening service game and though the two-time Wimbledon champion held, she fell 3-1 down when failing to win a point two games later.
It took Sabalenka just 29 minutes to forge ahead in the match, one of seven aces delivering the first set.
Kvitova had multiple chances to break in the fourth game of the second set but, in a game that lasted over 10 minutes, Sabalenka held firm before bending in a winner to break and go 4-3 up.
Sabalenka had three championship points and though Kvitova rallied to save all of those, two pieces of fortune via the net cord helped the Belarusian seal the win in one hour and 14 minutes.
"It's a special moment. It was an amazing week this week," Sabalenka said in her on-court interview.
"I was enjoying every second on the court."
While Pegula was taken to three sets by Maria Sakkari on Friday, world number one and defending champion Swiatek required only 56 minutes to score a 6-0 6-1 drubbing of Veronika Kudermetova.
In windy conditions in Doha, the top two seeds set up a Saturday showdown that will have plenty riding on it in terms of their rivalry.
When Swiatek lost to Pegula in early January at the United Cup in Sydney, winning only four games, the Pole was left in tears.
The rematch will either see Swiatek reassert her dominance over Pegula, or see the American show she has the 21-year-old's number for now.
Swiatek won all four matches she played against Pegula last season, with French Open and US Open quarter-finals victories among that set, but their last match has put a fresh spin on the head-to-head.
Crushing Kudermetova showed Swiatek at her ruthless best, and the world number one said: "I feel great. I was pretty worried how I was going to cope with the conditions today so I'm glad I played a smart way and I'm pretty happy I was so solid."
She is relishing the chance to test herself against Pegula again, saying: "It always takes a lot to win against Jessie. She's a great player, a really solid one, and we'll see, honestly. I'm not going to predict anything or over-analyse, I'll just play my best tennis."
Pegula overcame Greek fifth seed Sakkari 6-2 4-6 6-1 in the first semi-final.
While Swiatek will be chasing a 12th WTA-level singles title, the 28-year-old Pegula is after a third such trophy.
Speaking of the Sakkari match, Pegula said: "That was probably the hardest conditions I've ever had to play in, wind-wise. I played very smart."
