Collin Morikawa made history after clinching the US PGA Championship in San Francisco, while he became the third-youngest winner since World War II.

Morikawa celebrated a breakthrough on Sunday, claiming his maiden major title by two strokes in a thrilling finish at TPC Harding Park.

The 23-year-old posted a final-round 64 to finish 13 under for the tournament, ahead of Paul Casey and Dustin Johnson.

With back-to-back rounds of 65 and 64 for a 129 score, Morikawa recorded the lowest closing 36-hole tally by a major champion.

Aged 23 years, six months and three days, Morikawa also became the third-youngest champion of the major since 1946, only behind Jack Nicklaus (23 years, six months in 1963) and Rory McIlroy (23 years, three months and eight days in 2012).

Morikawa's six-under-par 64 in the final round also tied the lowest final-round score by a US PGA winner since Steve Elkington in 1995.