The 2018 LPGA Tour rookie finished the week at 17-under par, two-strokes ahead of 36 and 54-hole leader Pornanong Phatlum of Thailand.
With her father Wayne as her caddie, she came from a shot behind overnight Thai leader Pornanong Phatlum to post a 17-under 271 total and claim a first major title and the US$490,000 (S$669,000) winner's cheque.
"I've always joked by saying I haven't really won since turning pro and a major will be my first win and I can't believe it's actually true", the 22-year-old Hall told Golf Channel.
"I just got a huge knot in my throat and I just had to put my head down", he said after closing with a 1-under 69 for his first World Golf Championship title.
And no countrywomen has ever accomplished the biggest feat in her sport at such a young age - with one of the great final rounds by any European golfer, to boot.
Struggling to hold back the tears at the presentation, she said: "This is for you Grandad".
Hall finished on 17 under, having picked up five shots on the final day.
Despite her impressive ball striking and setting up of several opportunities, Ko had to settle with 10 successive pars in her third round, before birdying the 11th and 16th holes.
Hall tied for the lead with a 10-foot birdie at the 13th hole, before she and Phatlum both birdied the par-five 15th to remain locked together.
Georgia Hall became just the third British woman to win the Women's British Open major after Karen Stupples's 2004 and Catriona Matthew's 2009 victories.
"It was nearly like matchplay at the end, and I enjoy that sort of golf", said Hall.
"I was so confident coming into this event after past year".
'It's incredible. I had so much support today from all the people backing me and supporting me and cheering my name. He joined Dustin Johnson and Bubba Watson as three-time winners this season. It was very close up to the last two holes and I holed all the putts'. "I was a bit nervous but enjoyed it".
"I'm glad I finally played well around here, just in time to leave, " he said.
Phatlum's collapse meant Hall's bogey on the last mattered little, as she matched her best round of the week with a 67 to wrap up the win. Her playing partner, Sung Hyun Park, suffered throughout her final round. I went back every week to win the chocolate. Georgia played so wonderful today, everything is flawless.
"She is from here and everyone is rooting for her". "I'm not allowed to show any emotion because if I show I'm happy that's not right", dad Wayne said.
Hall and Pornanong Phatlum both played a stunning final round on Championship Sunday.
Hall shot a 5-under-par 67 in the final round to finish at 17-under 271 while becoming the fourth-youngest victor of the Women's British Open.
The galleries roared for the homeland woman as she made her way around the course.
The Thai 15-year-old closed with 77 for 12 over par.