After knocking on the door for more than a decade, the former Gold Coast high school prodigy landed her maiden major championship with a three-stroke triumph over fellow South Korean Jin Young Ko, American world No.2 Lilia Vu and Japan's Miya Yamashita.
Yang started the final round with a two-shot buffer and stormed to a seven-stroke lead at one point, before settling for a closing even-par 72 at Sahalee Country Club, east of Seattle.
She finished with a seven-under 281 total and the $US1.56 million winner's cheque.
Amy Yang is showered with champagne on the 18th hole at Sahalee Country Club. (AP PHOTO)
Ko (71), Vu (71) and Yamashita (73) shared the runner-up spoils at four under, one better than Americans Ally Ewing (71) and Lauren Hartlage (74).
Not even a three-putt bogey on the 16th hole and a watery double on No.17 could deny Yang after several near misses at the majors.
Yang, who completed her education at Robina State High and won the ANZ Ladies Masters at Royal Pines Resort as a 16-year-old while in Year 11, was runner-up at the US Women's Open in both 2012 and 2015.
Twice she held the 54-hole lead in majors, only to fall short.
The 34-year-old had also posted a total of five fourth placings at the PGA Championship, the Women's British Open and Chevron Championship.
Now, at age 34, Yang is the oldest major winner on the LPGA Tour since Angela Stanford won the 2018 Evian Championship at 40.
This was Yang's 75th major start, also the most before a player's first success since Stanford, who was playing her 76th.
"I'm lost for words right now," Yang said after saluting for the first time since winning last year's season-ending Tour Championship.
"So all the hard work we, our team, did together and I'm so grateful for that.
"I always wanted to win a major and I came close several times and I started doubting myself if I'm ever going to win a major before I retire.
"I've been on tour quite a while and I am so grateful and very, very happy to win a major."
Her reward for finally breaking through is a spot on South Korea's Olympic team for a third time.
Golf ace Hannah Green can't wait to represent Australia at a second Olympic Games. (John Cowpland/AAP PHOTOS)
Paris Games teammates Hannah Green (71) and Minjee Lee (74) finished as joint top Australians, in a tie for 24th at four over par.
The Perth duo, who will join men's representatives Jason Day and Lee's brother Min Woo in Paris, still have another major, the Evian Championship in France from July 11-14, before the Olympics.
Green, the world No.5 boasting two wins already in 2024, will head home for 10 days to recharge.
"It'll be really quick turnover, but it will be good for me mentally," she said.
"Not that I've been struggling in the last few months, but it's always nice to return home.
"Getting the (Olympics) opportunity in Tokyo was an amazing experience, albeit through COVID.
"Even so, I'm super excited for Paris to be alongside Minjee as well, both from Perth and we both played junior golf together.
"So it's really cool for us to both be there. Even her brother is in the team, so I think we have really good vibes for the Olympics."
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