The 34-year-old sailor crossed a virtual finish line drawn between the island of Ushant off France's northwest tip and Lizard Point in southwest England at 0145 GMT, comfortably beating the previous record set by compatriot Thomas Coville by six days and 10 hours.
Father-of-two Gabart becomes just the fourth title-holder for a world record of sailing the globe solo.
Since the record was first set in 2004, some 30 days have been shaved off.
The debut record holder was Frenchman Francis Joyon who completed the odyssey in 72 days and 22 hours.
British female sailor Ellen MacArthur took to the seas a year later, racing against the clock to break that record by just a day and a half (71 days, 14 hours).
She remained undefeated until 2016 when Coville set a new record of 49 days and three hours which many predicted would be difficult to topple.