Enable has completed a record third King George triumph at Ascot.
The mare - ridden by Frankie Dettori and trained by John Gosden - finished five-and-a-half lengths in front of second-placed Sovereign with the only other runner, Japan, way back.
Sovereign set the pace but six-year-old Enable reeled in the early leader and eventually cruised to victory.
"She's trained beautifully for this race and she is back in top order," Gosden said.
"We are thrilled with her and I was expecting to see that."
An emotional Dettori, who timed his attack perfectly to overhaul a tiring Sovereign in the home straight, said: "She's so consistent. She made it look so easy. She's six, she's not a spring chicken, so to put on a performance like that is great."
"I love her, she's touched my heart."
Japan had stalked Enable for the majority of the race but could not sustain the pace in the wet conditions.
Enable's bid to make history was made easier the day before the race when trainer Aidan O'Brien withdrew Anthony Van Dyck and opted to run Japan and Sovereign against the pre-race favourite.
Enable will now seek to make further history with a third win in the Prix de l'Arc de Triomphe at Longchamp in October.