The 34-year-old, a two-time Rugby World Cup winner with New Zealand, has switched codes again having signed a contract reportedly worth 9million Canadian dollars that will make him the highest-paid rugby league player in the world.
Williams, who featured for the All Blacks in their run to the World Cup semi-finals last month, began his professional career in the NRL with Canterbury Bulldogs.
After winning a Premiership with the Bulldogs, he switched to union to play for Top 14 club Toulon but returned to the NRL in 2013, winning a second title with Sydney Roosters.
It has been five years since Williams played league and his signing is a coup for a Toronto side that will spend next season in Super League having won promotion in just their third campaign.
— Toronto Wolfpack (@TOwolfpack) November 7, 2019
Centre Williams, a two-time World Cup-winner with the All Blacks with 58 caps to his name, is ready to play a big role for ambitious Toronto on and off the field.
"Toronto Wolfpack is a club that represents Toronto which is a very multicultural city," he said.
"The club has big ambitions and big goals. I want to be part of all this and do all I can to help reach those lofty goals.
"On the field I'd like to bring high quality play and do all I can for the betterment of the team. Off the field I'd like to use my experience to mentor the young players and be helpful where I am needed.
"Super league will be a new challenge and one I'm looking forward to. It will be a new experience and one I'm ready to embrace."
Photo Getty Images Caption: Sonny Bill Williams signs for Toronto Wolfpack