American Mark Wiebe overcame Bernhard Langer on the fifth play-off hole to win the Senior Open at Royal Birkdale.
After play had been halted because of darkness following two extra holes on Sunday, the tournament carried over to a fifth day.
Playing the 18th for a fifth time in the sudden-death play-off, Langer could not match the par four of the American.
German Langer, 55, let a two-shot lead slip at the 72nd hole on Sunday to allow Wiebe into the play-off.
Langer, a two-time winner of the Masters, had been three clear of the field going into Sunday, but took two shots to get out of a bunker at the last.
Rain and lightning caused play in the final round to be suspended on two occasions.
Both men wanted to finish the tournament on Sunday for scheduling reasons but, after they each parred the 18th twice, play was halted.
On Monday, Langer's approach on the fifth play-off hole landed just short of the green and, after chipping on, he missed with a par putt to keep the tournament alive.
The win, which earned the American £207,000 in prize money, is a sixth career victory for Wiebe, 55.
America's Corey Pavin, Peter Senior of Australia and South Africa's David Frost tied for third at six under par.