Ruud – the second seed – was too strong for Brit Norrie, winning 6-0 6-2 in Sunday's ATP 250 final.
Norway's Ruud earned his first hard-court trophy at the expense of Norrie and Tour-leading fifth title of 2021, ahead of world number one Novak Djokovic, US Open champion Daniil Medvedev and Olympic Games gold medallist Alexander Zverev (all four).
Ruud broke serve five times to boost his chances of qualifying for next month's ATP Finals in Turin.
"Special thanks to Rod, obviously the legend. I think you need to come to all my matches now because I'm playing really good when you come and watch," Ruud said after receiving the trophy from Rod Laver.
"I hope you will come to Indian Wells next week to watch, so let's see [what happens there]!"
The Norwegian, who is the top seed, saw off his opponent 7-6 (7-2) 6-3 to set up a quarter-final clash with home hopeful Federico Coria, who defeated Dusan Lajovic 4-6 7-5 6-4.
Ruud was taking to the court for the first time since being in ATP Cup action in early January, with ankle injury ruling him out of the Australian Open.
But on the scene of his maiden ATP title win in 2020, Ruud – who has won five tournaments since – looked in good shape.
"I feel, obviously, very good in Buenos Aires. I was a bit nervous coming back because it's the first time I have to defend a title," he said.
"Everything is a bit different since two years ago. When I won here it was a surprise. I was young.
"[This] was a good start. First time playing on clay in six months, so everything is a bit new again.
"Of course, I prefer to play on clay, but it takes some time to get used to the court and playing points."
Third seed Lorenzo Sonego also advanced through to the last eight in straight sets, the Italian beating Sebastian Baez 6-3 6-3 to set up a meeting with Fernando Verdasco.
Unseeded Spaniard Verdasco, seeking an eighth career title, progressed thanks to a hard-fought 2-6 6-3 7-5 win over Thiago Monteiro.
At the Dallas Open, John Isner won his opening match on home soil with a 7-6 (7-1) 6-7 (7-9) 7-6 (7-5) victory over Kevin Anderson.
Isner will next take on either Vasek Pospisil or Jurij Rodionov, with the qualifiers scheduled to meet on Thursday.
Marcos Giron and Jordan Thompson are also in the quarter-finals after seeing off Liam Broady and Brandan Nakashima respectively.
Having enjoyed the best season of his career in 2022, Ruud was bidding for his first trophy success of 2023 in Portugal, and the world number five made a flying start to his clash with Kecmanovic.
Ruud wrapped up the opener in just 36 minutes, taking control with a huge forehand winner to break in just the third game.
The Norwegian navigated two three-set contests in order to reach the showpiece, and it looked like another of his matches may go the distance when Kecmanovic recovered to force a second-set tie-break.
However, a dipping backhand saw Ruud secure the second of two crucial mini breaks, and he took the first of his three championship points to cap a fine week with silverware, sealing a 6-2 7-6 (7-3) win.
Elsewhere, Carballes Baena won just his second career title, triumphing on the clay in Marrakesh where he beat Alexandre Muller 4-6 7-6 (7-3) 6-2.
France's Muller showed no signs of being overawed on his first final outing as he took the opener in impressive fashion, but Carballes Baena edged a tie-break in the second before dominating the decider.
Carballes Baena's triumph – recorded in just under three hours – gave him his first title since the 2018 Ecuador Open, which also came on his favoured clay surface.
World number 10 Ruud prevailed 7-5 6-4 over the three-time grand slam winner, rolling to victory after a shaky start.
Murray broke Ruud in the 22-year-old's second service game of the match, but could not maintain the advantage as Ruud converted five of six break points in the match.
Ruud will face ninth seed Lorenzo Sonego, who defeated Sebastian Korda 6-4 6-3, saving six of seven break points against his own serve while converting all three of his chances on Korda's.
Fourth seed Denis Shapovalov defeated Taylor Fritz 7-6 (9-7) 6-2, saving six set points in the process.
The Canadian moves on to a quarter-final meeting with Cameron Norrie, who downed Daniel Evans 7-6 (7-3) 6-3.
Grigor Dimitrov dominated August Holmgren 6-1 6-1 in 56 minutes, winning 83 per cent of his service points.
Dimitrov next faces Aslan Karatsev, who rallied to upset fifth seed Hubert Hurkacz 5-7 6-4 6-2.
The 2022 US Open and French Open runner-up had struggled past Guido Andreozzi in the first round and followed up that up with a 7-5 2-6 7-6 (7-5) loss to Daniel.
The Japanese qualifier, ranked 125th in the world, won in just under three hours, winning the final three points of the deciding tie-break after Ruud led 5-4.
Ruud had more winners (38-32) but committed 30 unforced errors compared to Daniel's 12.
Taylor Fritz cruised into the last eight with a 6-4 6-4 win over Canada's Denis Shapovalov, setting up a quarter-final with sixth seed Francis Tiafoe, who eased past Feliciano Lopez 6-2 7-6 (8-6).
Fourth seed Holger Rune was too strong for Nuno Borges 6-0 6-2 inside an hour, while eighth seed Alex De Minaur crushed Jacopo Berrettini in just over an hour 6-1 6-0.
Top seed Lorenzo Musetti was a surprise second-round loser at the Chile Open with Jaume Munar triumphing 6-4 6-4 in one hour and 31 minutes.
Fourth seed Diego Schwartzman also bowed out, going down 6-4 4-6 7-6 (7-2) to local Nicolas Jarry.
Jarry will face Yannick Hanfmann in the quarter-finals, while Munar will take on Thiago Monteiro.
World number nine Ruud was a 7-6 (7-2) 7-5 winner against Reilly Opelka on Friday, putting him on the brink of a second ATP Tour crown of the season and a sixth in his past seven ATP 250 events on clay.
The Norwegian made the semi-finals at the Internazionali d'Italia last week and maintained his momentum ahead of the French Open.
He converted the match's only breakpoint in the penultimate game and sealed the deal in the next, dropping just five of 46 points behind his first serve throughout.
Ruud will take on Joao Sousa – who was the runner-up to Thomaz Bellucci in Geneva seven years ago – in the final after the Portuguese defeated Richard Gasquet 6-2 6-2.
Norrie will also be hopeful of making up for a past final defeat after winning his last-four encounter with Holger Rune at the Lyon Open.
The Briton was a set and a break up before Rune recovered to force a decider, which Norrie took for a 6-2 5-7 6-4 triumph in a little over two hours.
Norrie was beaten by Stefanos Tsitsipas in last year's final but it is Alex Molcan who stands between him and the trophy this time around.
Molcan, who is yet to win a Tour-level title, claimed an impressive victory 7-6 (7-2) 6-2 win over Alex de Minaur.
The world number 14 has been in incredible form on clay, having captured the Swedish Open and Swiss Open titles.
Ruud, who also landed the Geneva Open crown in May, has now won his last 11 matches, but was made to work hard for a 6-3 7-6 (9-7) victory over world number 91 Rinderknech in Kitzbuhel.
The Norwegian was forced to come from behind and defeat Sweden’s Mikael Ymer on Thursday, saving a match point in the process, and a single break swung a close opening set in his favour.
Fresh from defeating third seed Filip Krajinovic in the last eight, Rinderknech refused to lie down and took the second to a tie-break.
The big-serving Frenchman fired down 10 aces, but Ruud held his nerve to avoid a decider and prevail, saving a match point as he came from a mini-break down to extend his winning run.
The 22-year-old will play Pedro Martinez in the final after the Spaniard came from behind to beat Germany’s Daniel Altmeier 4-6 6-3 6-3.
Spaniard Martinez won 70 per cent of points behind his first serve and broke four times to move into the championship match.
Ruud made history with a comprehensive 6-1 6-4 victory over Portugal's Pedro Sousa in Sunday's final in Buenos Aires.
The 21-year-old also became the youngest Argentina Open champion – surpassing 2004 winner Guillermo Coria (22).
Ruud's win means he will become Norway's highest ranked male player ever – projected to climb to 34th – taking the record from his dad Christian, who reached 39th in the world in 1995.
Playing on red clay at the ATP 250 tournament, Ruud was a class above as he won all nine of his services games without facing a break point.
Ruud also broke three times in the one hour, 11-minute contest, including the first return game of the match to set the tone.
Sousa hit back-to-back double faults in the opening game of the second set to gift Ruud the break, and the eighth seed never looked back en route to a maiden crown.
The Norwegian, the beaten finalist at this year's French Open, made it successive triumphs at Roy Emerson Arena, after overcoming a first-set deficit to win 4-6 7-6 (7-4) 6-2.
It takes clay specialist Ruud to an eighth overall title on the surface and a third of the year, following victories at the Argentina Open in February and Geneva Open in May.
For Berrettini – also chasing a third title of the year after victory at the Stuttgart Open and Queen's – he will be left to rue letting his first-set advantage slip, after getting the drop on his rival.
The Italian was competing in his first event since he was forced to withdraw from Wimbledon with COVID-19, and made an impressive start under glorious sunshine on Sunday.
Yet Ruud was able to take him to the wire in the second set, before breaking his serve twice in the decider to emerge triumphant in Gstaad for the second year in a row in the end.
World number 14 Ruud is targeting a third successive ATP title, having also captured the Swedish Open and Swiss Open earlier this month.
It has been a timely return to form for the Norwegian, who suffered a shock defeat to Australia's Jordan Thompson at Wimbledon at the end of June.
Although he was in danger of seeing his nine-match winning streak come to an end in Kitzbuhel, after losing the opening set against Swedish opponent Ymer.
Ruud, who also triumphed at the Geneva Open in May, was then taken to a tie-break in the second ser by the world number 99, but held his nerve to tee up a decider.
It was one-way traffic from there with the 22-year-old dominating play to set up a last-four clash with Arthur Rinderknech, who hit five aces as he overcame third seed Filip Krajinovic 6-4 6-1.
Meanwhile, Daniel Altmaier's place in the semi-finals was secured with a 6-1 6-7 (5-7) 6-3 win over Gianluca Mager.
The world number 135, who reached the fourth round of last year's French Open, will play Pedro Martinez in the semi-finals after the Spaniard saw off Jozef Kovalik 6-2 6-2.
World number two Ruud lost 6-2 3-6 6-2 in Seoul on Friday as the Norwegian found the going too tough in his first tournament in Asia for three years.
Ranked 56th before this week, Nishioka is one win away from vaulting back into the top 50, potentially going beyond his highest ranking of 48th if he reaches the final.
He said, quoted on the ATP website: "I feel great. My motivation is very high. I am playing very well, very smart."
Assessing top seed Ruud, Nishioka said: "I know he came from Europe and played at the Laver Cup, which is not easy matches. He wasn't settled on this court or this country yet, maybe. I was ready. I was focused on playing against him and I had a plan and it worked."
Nishioka had an outstanding run to the Washington final in August, before losing out to Nick Kyrgios in the title match. That was a major outlier in his season, which has consisted largely of early-round defeats.
His semi-final opponent will be American Aleksandar Kovacevic, a 24-year-old world number 222 who is enjoying the biggest week of his career. A 'lucky loser', handed his place in the draw when a spot opened up, Kovacevic has taken full advantage and beat compatriot Mackenzie McDonald 4-6 6-3 6-2 in their last-eight battle.
Canadian Denis Shapovalov, still seeking a first final appearance of the year, moved one step away by beating Moldova's Radu Albot 6-2 6-2, setting up a clash with American Jenson Brooksby, who was handed a bye due to Cameron Norrie pulling out with illness.
The Norwegian needed just under 90 minutes to see off Coria, who was competing in his maiden tour-level final, getting the job done to win 6-3 6-3.
Ruud's electric start set the tone for the contest, as he raced into a 4-0 lead thanks to successive breaks – although Coria broke back to make it 4-1, his opponent's wobble was only brief.
Coria ensured the match was a little tighter initially in the second set, but Ruud's class showed as he rattled off three breaks on the trot and eventually converted his fifth match point in front of a joyous support.
"It was an incredible week, maybe the best week of my life," Ruud said after sealing the title without losing a single set.
"It's an incredible feeling playing here in Bastad with the Swedish, Norwegian and Danish support. There is nothing like that home crowd feeling.
"To win here means a lot. You get a little extra nervous as the No. 1 seed. Me and my father [former player Christian Ruud] have been joking about when I am going to beat him at this and this, and now I think I have beaten him in everything!
"The Ruud family can finally bring the trophy home to Norway. It is a special feeling having him here with me."
Ruud won the Nordea Open last weekend and added a fourth ATP Tour title of his career with a 6-3 6-2 defeat of Frenchman Gaston.
The Norwegian took his tally of tournament victories on clay this year to three, having also won the Geneva Open in May, and the 22-year-old will rise to ninth spot in the ATP Race To Turin on Monday.
Ruud saved nine of the 10 break points earned by first-time ATP Tour finalist Gaston, who only won 51 per cent of points behind his first serve.
Gaston, who had never been beyond the second round at an ATP Tour event before this week, was broken twice in each set as the 20-year-old was unable to halt Ruud's brilliant run on clay.
Left-hander Gaston broke straight back after Ruud went 3-1 up in the opening set but failed to back that up with a hold.
Ruud had as many as 16 break-point opportunities but got the job done in an hour and 34 minutes.
World number eight Rudd, who claimed the title in Geneva last year with a straight-sets final win over Denis Shapovalov, overcame Kokkinakis 6-4 7-6 (7-3) on Thursday and will now face Opelka.
The American bounced back from losing the second set against Dutchman Tallon Griekspoor to claim a 6-4 3-6 6-3 win as he bids for his third title of 2022, and second seed Ruud said he was excited to pit himself against Opelka after securing his spot in the semi-finals.
"I expect it to be tough," Ruud said. "But I will do my best and see how I can do. I always enjoy playing against Reilly. He is a similar age to myself, and it will be another battle against him – hopefully it will be a good one."
Elsewhere, three-time grand slam semi-finalist Richard Gasquet followed up his shock win over Daniil Medvedev with a 6-2 6-4 victory over Kamil Majchrzak, and will face Joao Sousa for a place in the final after the Portuguese beat Ilya Ivashka 7-5 7-5.
At the Lyon Open, top seed Norrie battled to a 6-4 4-6 7-5 win over Sebastian Baez, spurning three match points before finally downing the Argentinian after a marathon two hours and 40 minutes clash.
The world number 11 will face Holger Rune in his semi-final contest after the 19-year-old came from a set down to beat Manuel Guinard 3-6 6-3 6-4.
The other semi-final in France will see fourth seed Alex de Minaur take on Alex Molcan after the Australian's quarter-final opponent Yosuke Watanuki withdrew after losing the first set 6-4, citing a back issue.
Molcan, meanwhile, downed Federico Coria 6-3 6-2 to reach the final four.
Finn Ruusuvuori ousted the sixth seed with a 7-5 6-4 victory in Doha with a powerful display.
There were 26 winners from the racket of Ruusuvuori, who had only come out on top in one of his previous eight matches against top-30 opponents.
Ruusuvuori's next assignment will be a meeting with Jiri Lehecka, who saw off qualifier Damir Dzumhur 6-3 7-6 (7-3).
Roberto Bautista Agut, the fifth seed from Spain, saw the back of Marton Fucsovics 7-6 (9-7) 5-7 6-4.
Botic van de Zandschulp, Tallon Griekspoor and Soonwoo Kwon also made it through to round two.
Maxime Cressy had to dig deep to make it out of the first round of the Open 13, beating Geoffrey Blancaneaux 6-3 6-7 (5-7) 7-6 (7-4).
The fifth seed from the United States was joined in the last 16 by David Goffin, who defeated qualifier Lukas Klein 6-2 6-4.
Eighth seed Marc-Andrea Huesler made an early departure after going down in straight sets to Gregoire Barrere in Marseille.
The Argentinian was staring down the barrel of defeat when he lost the opening set and trailed 5-2 in the second, with Davidovich Fokina unable to convert a match point.
After his opponent failed to capitalise, Schwartzman recovered to win 2-6 7-6 (7-3) 6-1 to set up a semi-final with either Felix Auger-Aliassime or Yoshihito Nishioka.
Schwartzman is aiming to secure one of the final two spots for the ATP Finals and occupies the final qualifying berth.
"Tennis sometimes is crazy," said Schwartzman after the match. "Maybe today I got lucky to be here answering questions.
"But that is why I am here as well with this ranking, because I am always trying to find a way to win the matches. Today was not the exception to the rule."
Home favourite and top seed Alexander Zverev came through in three sets, beating Adrian Mannarino 6-4 6-7 (5-7) 6-4. He meets Jannik Sinner, who recovered from losing eight straight games to defeat Gilles Simon 6-3 0-6 6-4, in the other last-four match.
At the European Open, Dan Evans saved match point en route to ousting third seed Karen Khachanov 3-6 7-6 (9-7) 6-4 and will go up against Ugo Humbert in the semi-finals after the Frenchman beat Lloyd Harris in straight sets.
Alex de Minaur hammered Marcos Giron 6-3 6-0 in under an hour and faces Grigor Dimitrov next, with the Bulgarian handed a walkover after Milos Raonic withdrew before the match due to an abdominal strain.
Second seed Schwartzman, ranked ninth in the world, needed just 81 minutes to seal a 6-3 6-2 victory, setting up a third-round meeting with Alejandro Davidovich Fokina.
It was a less happy outing for third seed Shapovalov in Germany, the Canadian succumbing to a 6-1 4-6 6-2 loss against Gilles Simon.
The result represented a measure of revenge for Simon after the Frenchman lost to world number 12 Shapovalov in the first round of the French Open.
"I am really happy with the way I played, with the focus I had over all of the match," Simon said in his on-court interview.
"I am really happy to beat him, because it is a very, very good win. I had a tough match with him at Roland Garros. I lost it unfortunately, so I am happy that I am the winner this time."
Jannik Sinner awaits for Simon after he defeated Pierre-Hugues Herbert, while Yoshihito Nishioka also made it through.
At the European Open in Antwerp, top seed and home favourite David Goffin suffered a stunning 6-3 7-5 defeat to American qualifier Marcos Giron.
Giron's surprise victory put him in the last eight of a ATP Tour event for the first time and he saved 10 of 13 break points he faced for a maiden victory over a top-20 opponent.
Milos Raonic was not to be denied a place in the quarter-finals, though, and a 7-5 7-6 (7-4) defeat of Cameron Norrie means he will now meet Grigor Dimitrov.
After losing in his two previous finals in Argentina, Schwartzman finally came good in his home city of Buenos Aires with a 6-1 6-2 victory.
The world number nine was in complete control from the off, breaking six times and conceding on his serve just once as he took just 81 minutes to wrap up a fourth Tour title.
Cerundolo's run to the final had at least ensured that whoever came out on top in the showdown would result in the first Argentine champion of the competition since 2008, when David Nalbandian triumphed in a clash with compatriot Jose Acasuso.
"I'm very, very happy, it's been an amazing week for me," Schwartzman said in the trophy presentation.
"It's the first time that [I have won at] home. Two years ago, I reached the final here and lost. I was very unhappy, but two years later I have my revenge against Francisco who is a great player."
Schwartzman, the top seed in Buenos Aires, needed three hours, 41 minutes to edge Pablo Cuevas 5-7 7-6 (13-11) 7-5 in an epic battle at the ATP 250 tournament.
The Argentinian, last year's runner-up, saved four match points in the second set before overcoming Cuevas.
Schwartzman managed two breaks of serve in the deciding set, including the decisive one in the 12th game.
Awaiting him in the semi-finals is Pedro Sousa, the lucky loser continuing his run with a 7-6 (7-5) 6-4 victory over Thiago Monteiro.
Casper Ruud will face Juan Ignacio Londero in the other semi-final after their respective wins over Dusan Lajovic and Guido Pella.
At the New York Open, Opelka's title defence came to an end with a 5-7 6-4 6-4 loss to qualifier Jason Jung.
Opelka served 24 aces, but the 2019 champion was broken twice to fall to defeat in one hour, 52 minutes.
Jung will meet Andreas Seppi in a semi-final after the Italian veteran got past Jordan Thompson 6-7 (2-7) 6-4 6-1.
Kyle Edmund advanced thanks to a 3-6 6-2 7-6 (7-5) win against Kwon Soon-woo, while Miomir Kecmanovic beat Ugo Humbert 3-6 6-2 6-4.
The Argentine world number 14 had to overcome countryman Francisco Cerundolo 6-3 2-6 5-7 earlier on Saturday after their quarter-final had been interrupted by rain on Friday evening.
The match was tied at 1-1 in the third set when rain intervened, with Schwartzman triumphing when play resumed to earn a semi-final date with third seed Lorenzo Sonego.
Schwartzman would later beat Sonego 7-5 3-6 6-2 in almost three hours on a busy day for the 2020 French Open semi-finalist.
World number eight Ruud progressed with a routine 6-3 6-3 victory over Argentine sixth seed Federico Delbonis.
At the Dallas Open semi-finals, Reilly Opelka and John Isner broke the record for the longest tiebreaker on the ATP Tour since 1990.
Second seed Opelka triumphed over fellow American Isner but it was not easy, winning 7-6 (9-7) 7-6 (24-22).
Opelka sent down 39-21 aces across the match, earning a spot in the final against fourth seed Jenson Brooksby who beat Marcos Giron 6-4 6-7 (4-7) 7-6 (7-5).
