The tears of joy as the 22-year-old picked up the trophy were inevitable, as the realisation sunk in that she is only the third Briton to win this tournament since it was recognised a as a major and only the fifth British female to win a major of any description.
"I can't believe how many of you fans came out to support me, I am so grateful".
Georgia was born during the 1996 Masters won by Englishman Nick Faldo.
Hall was always chasing but was given hope when Phatlum bogeyed No. 8 to reduce her lead to one shot.
Hall joined Laura Davies (four), Alison Nicholas and Stupples as women's major winners from England.
Victory meant the 2013 British ladies' amateur champion, who now spends most of her time playing in America on the LPGA Tour, emulated compatriot Karen Stupples (2004) and Scot Catriona Matthew (2009), the other two British winners since this event became a major.
Over the 72 holes, Hall made only three bogeys - she could well afford the one at the last - and her six-birdie final round secured a two-shot victory over Pornanong. That gap became four, though, when that pair both birdied the par-5 15th before Hall went to the top of the leaderboard for the first time all week when she holed a 20-footer for yet another birdie at the 16th and wasn't going to be denied thereafter.
So Yeon Ryu would finish in 3rd position at 13 under, four from the victor and two behind Phatlum. Phatlum found trouble at the 17th and missed a short putt for bogey to give Hall a three-stroke lead with one hole play.
Sunday, Georgia Hall and Pornanong Phatlum were locked in a dramatic back and forth that felt more like match play than the final round of the Ricoh Women's British Open. The two-time major victor birdied three holes in a row from the fifth then added four more in five holes from the 11th to get to 13-under, three behind Hall and Phatlum.
Hall finished up with her only bogey of the day on the eighteenth but never looked likely to allow her lead to slip and joined Dame Laura Davies, Allison Nicholls and Karen Stupples as an English-born victor of the British Open.
"My long game wasn't quite on it today but my putter saved me and I'm just going to go out there and try to play every shot as it comes tomorrow".
It started from the outset, with Hall instantly applying pressure thanks to a fine clutch putt to make birdie at the first and take a share of the lead. I'm so happy she win, " the Thai said. McIlroy finished the front nine with consecutive bogeys and never recovered. A double-bogey 6 left Hall heading up the last with a three-shot cushion.
"Things could have certainly gone better", Woods said.
Also the 2014 and 2015 victor at TPC Twin Cities, the 57-year-old Perry matched Hale Irwin's tournament record of three victories in the final edition of the event that started in 1993 at Bunker Hills. "I'm just so grateful".