Sinner, the number one seed, moved into his fifth final of the season with a 6-2 6-2 defeat of Lloyd Harris in Antwerp.
The 20-year-old Italian, who is in the hunt for a maiden ATP Finals spot, dominated Harris from the baseline and saved all three break points he faced.
There were only 16 unforced errors from the racket of the composed Sinner, who will be bidding to win his fourth title of the season on Sunday.
Sinner said: "I am very happy to be in the final. I just love playing here and love playing indoors, so hopefully I can play a great match again tomorrow."
Schwartzman ended 20-year-old American Jenson Brooksby's impressive run with a 6-4 6-0 victory.
The Argentinian struck 15 winners and secured five breaks as he marched into the championship match.
Russian second seed Aslan Karatsev will come up against Marin Cilic in his first final on home soil after knocking compatriot Karen Khachanov out of the Kremlin Cup.
Karatsev beat Khachanov 7-6 (9-7) 6-1, while sixth seed Cilic – a two-time winner of the tournament in Moscow – got the better of Ricardas Berankis 6-3 6-4.
Sinner won his fourth title of what has been an outstanding season for the Italian in Antwerp last weekend and is only 110 points adrift of Hubert Hurkacz in the battle for the final place in the season-ending event in Turin.
Murray did the 20-year-old a favour by knocking Hurkacz out of the ATP 500 tournament in the Austrian capital on Monday and seventh seed Sinner eased to a 6-4 6-2 win over American Opelka two days later.
Sinner, who will overtake Pole Hurkacz if he reaches the semi-finals this week, won 93 per cent of points behind his first serve and did not face a break point in a resounding win and will play Dennis Novak in the second round.
Murray beat Alcaraz at Indian Wells this month, but the 18-year-old rising star from Spain turned the tables on the three-time grand slam champion with a 6-3 6-4 second-round win in Vienna.
Former world number one Murray struggled with his serve and was broken five times as he made an early exit.
Third seed Matteo Berrettini beat Nikoloz Basilashvili 6-7 (5-7) 6-2 6-3 to reach the third round, while Diego Schwartzman, Gael Monfils and Lorenzo Sonego moved into the second round.
In the St Petersburg Open, defending champion Andrey Rublev beat Ilya Ivashka 6-4 6-4 to reach the quarter-finals along with Denis Shapovalov, a 2-6 6-3 6-0 winner against Pablo Andujar.
Jan-Lennard Struff also moved into the last eight, with Karen Khachanov and Marin Cilic securing first-round wins.
In an all-American showdown, Fritz played a near-flawless match, converting 91 per cent of his accurate first serves into points while not allowing Sock a single break point opportunity.
Fritz will face seventh seed Marcos Giron in the quarter-final after the American defeated Germany's Oscar Otte 6-4 6-3, while the USA's John Isner also advanced past Germany's Daniel Altmaier 6-3 7-6 (7-1).
Earlier in the day, Serbian fourth seed Miomir Kecmanovic was upset by Ecuador's Emilio Gomez 2-6 7-6 (7-4) 6-4 to earn a crack at Isner in the quarter-finals.
Meanwhile, the top seed fell at the Cordoba Open as red-hot 21-year-old Juan Manuel Cerundolo shocked his Argentinian compatriot Diego Schwartzman 7-6 (8-6) 6-1.
It continues a remarkable run for Cerundolo – the defending champion in Cordoba – who has begun 2023 with 14 wins from his first 15 matches, while his older brother Francisco Cerundolo also advanced with a 6-3 3-6 7-5 win over Federico Delbonis.
If the two brothers both win their next two matches, they will meet in the final.
Federer teamed with long-time rival Rafael Nadal against American duo Frances Tiafoe and Jack Sock as Team Europe face Team World at the O2 Arena.
After winning the first set, the Swiss and the Spaniard were faced with a spirited fightback from Tiafoe and Sock, who won a second-set tie-break before also clinching the match tie-break to seal victory 4-6 7-6 (7-2) 11-9.
There had been a great atmosphere in London on Friday for the fifth edition of the three-day competition.
Federer, 41, had not played a match since he was knocked out of Wimbledon by Hubert Hurkacz at the quarter-final stage last year due to knee injury.
There were huge cheers when Federer and Nadal came onto the court and loud roars for the Swiss great when he came up with his first winner.
There was a sensational moment in the first set when Federer appeared to have won a point after his shot hit the top of the net and bounced in, only for a replay to show the ball had somehow been hit through a small hole between the net and the post, meaning Team Europe lost the point, despite the remarkably unlikely event of the ball passing through such a gap.
Novak Djokovic and Andy Murray were among Federer and Nadal's team-mates offering some tactical input between games, and the legendary duo had to save a first break point of the match before the Spaniard held to put them 5-4 up.
It was two of the all-time greats that took a tight opening set when Sock put a volley into the net, prompting Team World captain John McEnroe to tell his doubles pair they appeared to be getting "caught up in the hoopla."
A determined Team World managed to level it up after a back-and-forth second set went to a tie-break, with Tiafoe and Sock coming out on top with their superior power and pace.
That took it to a dramatic deciding match tie-break, with every point keeping fans holding their breath, including some trademark Federer magic at 6-7 when he diverted a Sock shot across court for a crowd-pleasing winner.
It looked like the dream script was being followed as Federer served at match point for himself and Nadal, but the former could only hit a shot into the net, before Sock and Tiafoe won the next two points to secure the win for Team World.
It was then hugs all round as respect was paid to the 20-time grand slam winner at the conclusion of a phenomenal career.
Earlier in the day, Casper Ruud drew first blood for the Team Europe, beating Sock 6-4 5-7 10-7, before Stefanos Tsitsipas doubled their advantage with an emphatic 6-2 6-1 defeat of Diego Schwartzman.
There was drama after the first set of that second singles match when a protester, wearing a T-shirt with the message, "END UK PRIVATE JETS" on, set their arm alight on court before being escorted out by security.
Alex de Minaur then got Team World on the board with a 5-7 6-3 10-7 success over home favourite Murray before the late-night main event under the lights.
Alcaraz, featuring in an ATP Masters 1000 event for just the second time, was in impressive form as he saw off France's Adrian Mannarino 6-4 6-0.
The teenager, who will face Nadal on his 18th birthday on Wednesday, fired 19 winners as he took the initiative against his more experienced opponent and his reward is significant.
He became the tournament's youngest ever match winner, beating the record set by Nadal.
"For me, [to] play against Rafa is a dream come true," Alcaraz said as he readies himself to go up against the 20-time grand slam winner.
"Since I was a kid, I wished to play a match against Rafa and now I will be able to here [on] the Centre Court of La Caja Magica in Madrid. It is a really special match against Rafa."
He told Tennis Channel: "It's the best present for my birthday."
The biggest casualty of the day was 13th seed Grigor Dimitrov, who lost 3-6 6-3 7-6 (7-5) to Lloyd Harris early on, the South African now 4-0 against top-20 opponents this year.
Two qualifiers in Pablo Andujar and Marcos Giron played out a remarkable encounter that lasted three hours and 21 minutes.
The first set alone clocked in at just over an hour and a half, but eventually Giron came through the gruelling clash 6-7 (8-10) 7-6 (7-4) 7-5 to set up a meeting with third seed Dominic Thiem.
Fabio Fognini defeated Carlos Taberner 7-6 (7-4) 2-6 6-3 for the right to face eighth seed and Italian countryman Matteo Berrettini.
Diego Schwartzman, the seventh seed, awaits Aslan Karatsev after he beat Ugo Humbert in straight sets in what was the Russian's debut appearance at the tournament.
Dan Evans and John Isner were among the other players to secure progress on Monday.
Thompson overcame big-serving American Isner – who had a first-round bye – 7-6 (7-2) 6-7 (3-7) 6-3 in New York on Thursday.
Isner was playing his first match since being forced to retire from his third-round clash against Stan Wawrinka at the Australian Open due to a foot injury.
Thompson lost to Isner in last year's New York quarter-finals but the Australian turned the tables after two hours, 31 minutes.
"I'm pretty stoked about that. That was a tough match," Thompson said. "I didn't get too many looks at Isner's serve, but managed to get the one break and held onto it."
Standing in the way of Thompson and the semi-finals is Andreas Seppi.
Opelka opened his title defence by cruising past Yoshihito Nishioka 6-4 6-4 at the ATP 250 tournament.
Next up is qualifier Jason Jung, who stunned seventh seed Cameron Norrie 6-4 6-4, Kyle Edmund – the eighth seed – was too good for German Dominik Koepfer 6-2 6-4.
At the Argentina Open in Buenos Aires, Diego Schwartzman and Guido Pella moved through to the quarters on clay.
Schwartzman – the top seed – prevailed 6-3 4-6 6-2 over Federico Delbonis and second seed Guido Pella survived a marathon against Facundo Bagnis 7-6 (7-2) 6-7 (2-7) 6-4.
Fellow seeds Laslo Djere and Albert Ramos-Vinolas, however, crashed out following defeats to Juan Ignacio Londero and Pablo Cuevas.
Fognini, competing for the first time since undergoing arthroscopic surgery on both ankles in May, went down 6-1 6-2 to world 303 Huesler in a little under an hour.
The 2011 French Open quarter-finalist was broken in the second game and Huesler, who had just two previous career wins on the ATP Tour, broke again in the sixth.
After saving three break points in the early stages of the third set, Huesler held serve and secured a famous win in Kitzbuhel with minimal fuss.
Feliciano Lopez awaits in the last eight after battling to a 7-5 6-7 (4-7) 7-6 (7-3) victory over seventh seed Guido Pella in three hours.
World number 14 Schwartzman triumphed 6-3 6-2, converting three of five break points to win in one hour and 10 minutes.
Schwartzman will face Colombian lucky loser Daniel Elahi Galan who progressed with a 6-2 3-6 6-1 victory over Jaume Munar.
Eighth seed Pedro Martinez was eliminated by Argentina wildcard Juan Ignacio Londero 6-3 7-6 (7-3).
Londero will face Serbian Nikola Milojevic, another lucky loser, who got past wild card Tomas Martin Etcheverry 6-3 7-6 (7-4).
Greek star Tsitsipas flexed his muscles in a straight-sets win over Damir Dzumhur on Saturday.
Australian Open semi-finalist and Dubai Tennis Championships winner Karatsev enjoyed a victorious Miami debut.
Andrey Rublev, Diego Schwartzman, Denis Shapovalov, Marin Cilic and Milos Raonic also progressed at the ATP 1000 tournament.
TSITSIPAS STAYS HOT
World number five Tsitsipas eased past Dzumhur 6-1 6-4 in his first appearance since losing in last week's Mexican Open final.
Tsitsipas (15-4) became the third player to reach 15 wins this season, the second seed following in the footsteps of Russian duo Rublev (17-3) and Daniil Medvedev (15-2).
"It was a great match, especially against a guy that I probably don't have a good record playing against in the past," said Tsitsipas. "I started the match very strong, breaking him twice and taking a big lead in the score, and I think the things worked out by themselves after that."
Tsitsipas will face Kei Nishikori after the Japanese outlasted Aljaz Bedene 7-6 (8-6) 5-7 6-4.
NO STOPPING KARATSEV
Karatsev's Miami Open debut ended in a 6-4 6-3 win for the 17th-seeded Russian over Mikhail Kukushkin.
Already in the ATP's top 100 and set to keep climbing, Karatsev broke serve four times en route to the next round, where Sebastian Korda awaits after upstaging 10th seed Fabio Fognini 1-6 6-4 6-2.
"Of course it gives me confidence to win my first title, but you arrive here and it’s a different surface and new tournament," said Karatsev, who ended last season ranked 112th before bursting into the top 30 behind his semi-final run at Melbourne Park. "So you try [to think of it] as a new tournament and new place, but of course it gives me a lot of confidence."
Karatsev owns a 13-2 record this year, with his only two losses coming against world number one Novak Djokovic and US Open champion Dominic Thiem.
RUBLEV ROLLS ON
Fourth seed Rublev has proven to be remarkably consistent, highlighted by his crushing 6-1 6-2 rain-interrupted victory against Tennys Sandgren.
Having equalled his previous best run in Miami, Rublev will play 29th seed Marton Fucsovics who took down Thanasi Kokkinakis 7-6 (7-3) 6-7 (4-7) 6-4.
Rublev has won a Tour-leading 17 matches this year.
Elsewhere, fifth seed Schwartzman was a 6-3 6-3 winner against Yasutaka Uchiyama, Shapovalov – the sixth seed – trumped Ilya Ivashka 6-7 (5-7) 6-4 6-4 in a marathon, 12th seed Raonic accounted for Jordan Thompson 6-2 6-1, former US Open winner Cilic surprised 13th seed Christian Garin 3-6 7-5 7-6 (7-5), while 15th seed Alex de Minaur was eliminated.
Greek star and second seed Tsitsipas got the better of 2014 US Open runner-up Kei Nishikori in Miami.
Rublev continued his fine 2021 with a straight-sets demolition of Marton Fucsovics at the ATP 1000 tournament.
In-form Aslan Karatsev, however, bowed out following a surprise loss to Sebastian Korda.
TSITSIPAS HALTS NISHIKORI
Despite a mid-match wobble, Tsitsipas overcame Nishikori 6-3 3-6 6-1 to reach the fourth round.
Former world number four Nishikori forced a deciding set but Tsitsipas withstood the Japanese's comeback.
Tsitsipas, who hit 32 winners, will meet Lorenzo Sonego for a place in the quarter-finals after the 24th seed defeated Daniel Elahi Galan 7-6 (8-6) 6-3.
RUBLEV STAYS HOT
Russian fourth seed Rublev made light work of Fucsovics 6-2 6-1 in just 52 minutes.
Rublev leads the ATP Tour with 18 victories this season after eliminating the in-form Hungarian, ahead of top seed Daniil Medvedev (16-2).
The result secured a third win for Rublev over 29th seed Fucsovics this month.
"I was laughing, because of [the] situation and plus Marton also told me, 'I don't want to see you. I don't want to see you'," Rublev said, cracking a laugh. "[It was] just a situation that [was] fun, and I feel sorry."
Awaiting Rublev is 2014 US Open champion and former world number three Marin Cilic, who beat Lorenzo Musetti 6-3 6-4.
KARATSEV CONQUERED
For only the third time this year, Australian Open semi-finalist and Dubai Tennis Championships winner Karatsev tasted defeat following a 6-3 6-0 loss at the hands of Korda.
American sensation Korda became the first player outside the top five to beat Karatsev this year, with the latter's previous two losses coming against world number one Novak Djokovic and world number four Dominic Thiem.
"It is super special [to reach the Round of 16], especially playing a guy who was as hot as he was," said Korda. "I just took the tactics that I used [against him] at Roland Garros and it worked out really well today."
Diego Schwartzman stands in the way of Korda and the quarters after the fifth seed accounted for Adrian Mannarino 6-1 6-4.
Elsewhere, Denis Shapovalov – the sixth seed – was upstaged by Hubert Hurkacz 6-3 7-6 (8-6).
Another Canadian awaits Hurkacz after 12th seed Milos Raonic was a 6-4 7-5 winner against Ugo Humbert.
Medvedev – the US Open champion – has lost only three of his last 41 sets, and has never dropped one to McDonald in five career meetings with the American as he maintained his red-hot form.
Russian star Medvedev is now 37-5 on hardcourts this year and appears well-positioned to make it past the third round of the ATP Masters 1000 tournament for the first time as he awaits Filip Krajinovic.
"I'm actually really pleased, because usually I haven’t played well in Indian Wells and I haven’t been playing that well in practices before [the tournament]," Medvedev said in his on-court interview. "[I am] really happy with my performance. That’s the most important [thing] no matter how I played before the tournament."
RUBLEV ROLLS PAST TABERNER
Medvedev's countryman Andrey Rublev closed out the night session with a 6-3 6-4 defeat of Carlos Taberner, who was facing a top-10 opponent for the first time.
Fourth seed and world number five Rublev won 66 per cent of points on his first serve and hit 30 winners to Taberner's 12.
Rublev improved to 47-16 this season, 31-9 on hard courts, and will face Tommy Paul in the third round.
SHAPOVALOV WINS IN NEAR-WALKOVER
Most of the seeded players in action had an easy time of it, none more so than Canadian ninth seed Denis Shapovalov.
Shapovalov's opponent and countryman Vasek Pospisil retired with an apparent back injury after dropping the first three games of the match.
Sixth seed Casper Ruud blew past Roberto Carballes Baena 6-1 6-2, while eighth seed Hubert Hurkacz downed Alexei Popyrin 6-1 7-5.
Diego Schwartzman had to work harder to advance, the 11th seed outlasting qualifier Maxime Cressy 6-2 3-6 7-5.
Top-ranked American Reilly Opelka, the 16th seed, beat Taro Daniel 7-5 6-3 for his first main-draw victory at Indian Wells in four attempts.
Daniel Evans also went the distance to defeat Kei Nishikori 4-6 6-3 6-4, while former world number three Grigor Dimitrov, 2021 Australian Open semi-finalist Aslan Karatsev and Frances Tiafoe were among the other players to advance.
Three-time grand slam winner Wawrinka, who is the oldest player in the main draw, hit back in the Spanish capital to progress 6-7 (7-3) 6-3 7-6 (7-4).
The 38-year-old won 46 of 54 first-serve points and now has a couple of days to recover before facing fifth seed Rublev, who was handed a bye to the last 32.
Roberto Carballes Baena is also through after defeating David Goffin 6-4 6-4, with Alexander Zverev up next, while Alex Molcan saw off Wu Yibing 6-2 6-4.
There was a shock elsewhere on Wednesday as Diego Schwartzman was downed in straight sets by Hugo Grenier.
Zverev, who is ranked third in the world - two places higher than Tsitsipas - fought back to defeat Jannik Sinner 5-7 6-3 7-6 (7-5) in his quarter-final match, denying his opponent another top-five seed scalp following his prior win over Andrey Rublev.
"It means a lot, definitely, especially [with] how this year has been going so far for me," said Zverev after a gruelling three hours on court.
"I've lost long matches like that, so I’m happy I won this one."
Tsitsipas also orchestrated a superb turnaround against Diego Schwartzman, prevailing 6-2 6-7 (3-7) 6-4.
The Greek had looked set for a last-eight exit at four games down in the final set, only to stage a dramatic comeback to keep his hopes of a first title since last May's Lyon Open alive.
"There was a moment in the match where I felt what I was doing wasn't working," Tsitsipas said.
"He had a massive lead and momentum in what he was trying to do. I just tried to stay in the match as much as I could and that worked out very well.
"I wasn't expecting much at that point being a double break down, so I relaxed at that point."
Schwartzman meanwhile will rue his inability to put the tie to bed, having already reached two ATP finals this year.
Grigor Dimitrov and Alejandro Davidovich Fokina will face off in the other semi-final.
Bulgarian Dimitrov beat off Hubert Hurkacz in another final-set tie-break, winning 6-4 3-6 7-6 (7-2).
Fokina, who eliminated Novak Djokovic in the second round, turned over Indian Wells champion Taylor Fritz in another comeback result, triumphing 2-6 6-4 6-3.
World number seven Zverev beat Felix Auger-Aliassime to claim the Cologne Indoors title on October 18 and continued his fine form in the city with a 6-2 6-1 triumph on Sunday.
Schwartzman had denied Auger-Aliassime the chance to avenge his previous defeat but was never a match for in-form Zverev, who hit nine aces – to his opponent's zero – and saved the only break point he faced.
After an even start, Zverev nosed himself ahead with a break of Schwartzman's serve in the fifth game of the opener, with another concession from the Argentine following.
Zverev swiftly wrapped things up with his first set point, though Schwartzman rallied to gain a break point in the opening game of the final set.
It was an opportunity the world number nine failed to grasp, however, and Zverev made him pay with some clinical shots, rounding off the victory – and his second title of 2020 – with a supreme forehand down the line.
The 23-year-old lost to Sinner at the last-16 stage of the French Open earlier this month but was too strong for the wildcard entrant in this latest match, prevailing 7-6 (7-3) 6-3.
Zverev, who carried a hip injury into the contest, lost serve in the fourth game but responded well and converted his first match point with a blistering serve.
He held throughout the second set and will now face Diego Schwartzman, who beat last week's beaten Cologne Indoors finalist Felix Auger-Aliassime in the other semi.
Second seed Schwartzman came out on top 6-4 5-7 6-4 in two hours and 31 minutes to reach his third final of 2020, converting four of five break points.
Ugo Humbert saved four match points against Dan Evans on the way to reaching the European Open final in Antwerp, meanwhile, battling to a 4-6 7-6 (9-7) 6-4 victory.
The opportunities for Evans all came the Briton's way in a second-set tie-break, with Humbert coming back from 6-3 behind and then 7-6 in the breaker to keep his hopes alive.
He found a way to level the match before edging the decider, with the 22-year-old French left-hander sealing his place in a second final of 2020 after winning in Auckland back in January.
It took him three hours and 14 minutes to complete the task, but at least Humbert had the evening off as Alex de Minaur and Grigor Dimitrov battled it out to join him in the final.
And it was eighth-seeded Australian De Minaur who claimed the victory in a tight match that lasted two hours and 48 minutes.
De Minaur held his nerve to triumph 7-6 (7-4) 6-7 (3-7) 6-4 to reach his first tour-level final in 12 months, losing to Roger Federer on the previous occasion at the Swiss Indoors Basel.
