Dominic Dale beat fellow Welshman Ryan Day 10-6 in the Shanghai Masters final to win his first title in 10 years.
Dale's two ranking final wins have both been major upsets
World number 16 Day, 27, made a strong start, two century breaks from the Bridgend man helping him to a 6-2 lead.
But Neath's Dale stormed back to win the final eight frames, with a break of 143 in the 10th, to claim the £48,000 prize at the 8,000-seater Grand Stage.
The 35-year-old's only previous ranking final was a 9-6 win over John Higgins in the 1997 Grand Prix in Bournemouth.
Dale pocketed an extra £2,000 for the highest break of the tournament, his 143 overhauling the 133 Ian McCulloch made against Shaun Murphy in the first round.
The showdown was the first all-Welsh ranking final since Mark Williams beat Matthew Stevens 18-16 at the 2000 World Championship.
I'm here 10 years after winning my first title and it means so much to me
Dale, known as the "Spaceman", is up to 31st in the world rankings, his first time in the elite top 32 for two years, and the Shanghai win moves him to 16th in the provisional list.
"I was a bit down when Ryan went 6-3 up, but I just kept telling myself that I could come back," said Dale.
"I felt really good throughout the match, but I knew I had to play well because Ryan is such a good player.
"He deserved to be 6-3 up after the afternoon session, but I never dreamed that I could have produced a comeback like that. It's all a bit of a blur!
"I'm here 10 years after winning my first title and it means so much to me. I'm still competing with the best players.
"I can't wait for 2017 now! But seriously, I want to be more consistent with my form and get into the top 16."
Hopefully I can build on what I've started here this week
A 100-1 outsider for the title at the start of the tournament, Dale says his upturn in form was sparked by a new cue he started using in June.
His practice partner Day, appearing in his second ranking final following a 9-4 defeat to Murphy in this year's Malta Cup, will be consoled by a £22,500 runners-up prize.
"I was very comfortable in the opening session, but Dominic had his 143 break in the first frame after the break and that settled him," said Day.
"The balls went his way, but it was a great comeback. He ended on a high note in the first session and then played very well later on. I still felt comfortable, but I couldn't settle for some reason.
"It's been a good week and I've won a lot of matches. Hopefully I can build on what I've started here."
Day, who managed to score just 71 points in the last eight frames of the match, moves up six places in the provisional rankings to number 10.