New Zealand heavyweight boxing champion Sonny Bill Williams' next fight has been confirmed for Brisbane next month against South African veteran Francois Botha.

Fight promoters announced World Cup-winning All Black Williams will fight Botha on November 24.

Botha, 44, has won 48 fights, lost eight and drawn three in a professional career that includes a fifth-round knockout at the hands of former world champion Mike Tyson.

Williams told the Sydney Morning Herald that Botha would be a sterner opponent than anybody he has fought in a fledgling career.

"It's a bit of a daunting prospect but I believe it's a step in the right direction for my boxing," he said.

"A lot of people will be saying I've bit off more than I can chew this time but I'll be looking to do what I've done last fight."

Williams said the Wild Knights club had freed him up for boxing training sessions most mornings, to complement his rugby duties in the afternoon.