Phil Mickelson, at 50, Wins P.G.A. Championship

Mickelson, who will turn 51 next month, became the oldest winner of a major golf tournament after a tense final round on the treacherous Ocean Course at Kiawah Island.

KIAWAH ISLAND, S.C. — Weathering a riveting, roller-coaster test of nerve over five hours, Phil Mickelson, who will turn 51 next month, won the P.G.A. Championship on Sunday to become the oldest golfer to win a major championship. The record was previously held by Julius Boros, who was 48 when he won the 1968 P.G.A. Championship. Mickelson shot six under par for the tournament, finishing two strokes ahead of the runners-up, Brooks Koepka and Louis Oosthuizen. Mickelson becomes the latest in a growing group of sports stars who have defied traditional retirement ages for athletes and proved that championships can still be won in careers that last into middle age. Mickelson has followed the lead of Tom Brady, who won his seventh Super Bowl title three months ago at 43. Serena Williams has remained consistently in the hunt for elite titles at 39, an age that historically has seen tennis players recede to a senior circuit. Tiger Woods, although seriously injured in a car crash in February, won his fifth Masters tournament two years ago at 43.