The 31-year-old Irishman left 'Cowboy' Cerrone bloodied just seconds into the fight by ramming shoulders into his face before landing a head kick that stunned his opponent.
McGregor then pounded strikes into a downed Cerrone before referee Herb Dean called a halt to the action.
The victory was McGregor's first since November 2016 at Madison Square Garden when he beat Eddie Alvarez to win the lightweight title and become the organisation’s first simultaneous two-weight champion.