As Business Insider previously reported, the previous record for most expensive work sold by a living artist was Jeff Koons' orange "Balloon Dog," which sold for $58.4 million in 2013.
The buyer's premium and commission took the final price for the canvas, which adorned the wall of the bidding room, to Dollars 90,312,500, the auction house announced.
However, it wouldn't be until Hockney went through a bad split with Schlesinger in 1971 that the idea of the painting would come to the former.
But, while grappling with the breakdown of their relationship, Hockney realized after months of work that he wasn't happy with the composition - the angle of the pool was all wrong.
He added: "I always say in the studio I don't feel old, I just feel 30".
Christie's described it as "one of the great masterpieces of the modern era".
"Absolutely!" Christie's Alex Rotter told AFP when asked if the picture was really worth Dollars 90 million.
"The strategy was new to everyone, including us", said Loic Gouzer, Christie's chairman of postwar and contemporary art.
"This is the trophy piece by one of the greatest living artists now, if not the greatest living artist", he added. It has been long held by a private collector.
The Hockney sale, a "differnet kind of trophy", shows a "new demand for living artists", notes The New York Times.
Portrait of an Artist (Pool with Two Figures), features a man in a peach blazer standing on a sunlit ledge and peering over the rim of a pool at a submerged swimmer. The buyer was not immediately revealed.
Mr Lewis, a currency trader who owns football team Tottenham Hotspur, declined to accept a guarantee despite offers of about US$80 million, according to people familiar with the matter.
A visitor views "Portrait of an Artist (Pool with Two Figures)", a 1972-painting by David Hockney, during a press preview for the British artists' retrospective at Tate Britain in London, England, Feb. 6, 2017.
Do you have a favorite Hockney piece?