Cameron Norrie became the first Briton to win the Indian Wells title when he fought back from a set and a break down to beat Nikoloz Basilashvili.
Norrie, 26, won 3-6 6-4 6-1 against the Georgian to seal one of the biggest titles in tennis.
"I'm so happy, I can't even describe it," he said on court.
His exploits in California have propelled Norrie to British number one and he is in the running to reach the elite season-ending ATP Finals.
Norrie will rise to a career-high 16th in the world, having started the year ranked 74th, after a stunning season where he has reached six finals and won 47 matches.
Norrie had led in the first set with an early break but was pegged back as the big-hitting Basilashvili took charge. But the Briton, whose resilience and fitness have been the hallmark of his successful year, broke to love to level and force a deciding set.
The left-hander broke early in the third and saved three break points on his serve to take a 3-0 lead as unforced errors began to mount for the Georgian world number 36, who eventually sent a forehand long on championship point to hand Norrie the biggest title of his career.
"I can't really believe it. If you'd have told me I'd have won before the tournament started I wouldn't have believed you, so it's amazing," said Norrie, who is the first British player to reach the final at one of the elite Masters 1,000 events since Andy Murray won in Paris in 2016.
- Who 'threw away' Norrie's shoes before final?
- Badosa wins Indian Wells on debut
- Raducanu to train with Konta's ex-coach
Norrie achieves a British first
Norrie's win comes just a month after compatriot Emma Raducanu's stunning US Open victory as British tennis enjoys something of a resurgence.
While Raducanu's rise to British number one was sudden and dramatic, Norrie's path to the top has been more understated and built on consistency.
Only world number one Novak Djokovic has been in as many finals this year as Norrie, whose versatility has taken him to finals on hard, clay and grass courts.
His maiden ATP singles trophy came in July when he won the Los Cabos Open in Mexico and he has now backed that up with one of the most prestigious tour titles outside the four Grand Slams.
He has also achieved something that no other Briton has, with Murray, Tim Henman and Greg Rusedski all having reached the Indian Wells final but finishing as runners-up in California.
He is 10th in the race to qualify for next month's eight-man ATP Finals in Turin and with eighth-placed Rafael Nadal missing the rest of the season, Norrie is within touching distance of overtaking ninth-placed Hubert Hurkacz and booking a spot.
He is scheduled to compete in events in Vienna and Paris next as he seeks to gather enough points to complete what would have been considered an unlikely feat at the start of the season.
Norrie dedicates victory to parents
The very best of Norrie's game was on display at 5-4 in the second set when the Briton produced a delightful drop-shot and lob combination, as well as an inside out forehand volley, to set up a break to love and a total swing in momentum.
After breaking early in the third he then had to fend off three break points to go 3-0 up and he then never looked back as Basilashvili came back from a bathroom break to put in a poor service game that left Norrie serving for the match.
The Briton needed only one of his two championship points to secure the win as the errors kept coming off Basilashvili's racquet.
"For a stage he went through and hit so many winners. It was tough for me to get some confidence. The rallies were really short and he was just blasting winners," said Norrie,
"When I made a couple of big shots in the 5-4 game in the second set it gave me a lot of confidence, and I was able to find my feet again, start moving again, and make the rallies physical like I've been doing all tournament and it worked in my favour."
Norrie, whose only struggle of the day was when he was trying to lift the heavy glass trophy, dedicated his victory to his parents.
Born in South Africa, Norrie has a Scottish dad and Welsh mum, and was brought up in New Zealand before playing college tennis in the United States.
While many of his peers took the more conventional route from junior tennis to the professional Futures circuit, Norrie chose to combine his sport with studying for a sociology degree, in order to have a more "normal life".
BBC tennis correspondent Russell Fuller
Basilashvili is known for his ferocious power, and Norrie was in danger of being overwhelmed when he dropped serve early in the second set.
But the 26-year-old knuckled down, broke to win the set with some attacking brilliance and then drove the Georgian to distraction with some breathtaking defence in the decider.
All the more impressive when you learn the shoes he had left on top of his locker disappeared overnight, leaving him to break in a new pair in the biggest match of his life.
The greatest triumph of Norrie's career leaves him within 160 points of the man currently in the final qualifying spot for the ATP Finals.
It is a lot to ask him to continue in the same vein after switching continents, and with no time for rest, but he is entered in tournaments in Vienna, Paris and Stockholm before the season is out.
- All About Michael Holding: Listen to a revealing conversation with one of cricket's defining voices
- The best of the Bond villains: Exploring the memorable music that made 007's foes