Sonny Bill Williams has won the New Zealand Professional Boxing Association heavyweight title after a first-round stoppage of American Clarence Tillman in Hamilton.

After a cagey start by both boxers on Wednesday night, Williams produced a left hook late in the round that had Tillman wobbling.

The 26-year-old All Black landed a series of further blows before the referee stopped the scheduled 10-round contest.

The win takes Williams’ fight record to five wins from five bouts.

The loss was the 34-year-old Tillman’s ninth of a career that has included 11 wins and two draws.

Williams, who has also been a Kiwi rugby league representative, now turns his attention to the Super rugby competition with the Chiefs.