Sonny William Williams (born 3 August 1985) is a New Zealand professional rugby league footballer who plays as a second-row forward for the Toronto Wolfpack in the Betfred Super League, and New Zealand at international level.
He is a former professional rugby union footballer and heavyweight boxer. He is only the second person to represent New Zealand in rugby union after first playing for the country in rugby league, and is one of only 20 players to have won multiple Rugby World Cups.
Williams began his career in rugby league, and played as a second-row forward over seven seasons in two spells in the National Rugby League (NRL), with the Canterbury Bulldogs and Sydney Roosters. He has won 12 caps for New Zealand (the Kiwis) and won the RLIF Awards for Rookie of the Year in 2004 and International Player of the Year in 2013.
He first moved to rugby union in 2010 and had spells playing for Toulon in France, Canterbury, Counties Manukau, the Crusaders, Chiefs and Blues in New Zealand and Panasonic Wild Knights in Japan. He won 58 caps for New Zealand (the All Blacks), and was part of the teams that won the 2011 and 2015 World Cups. He has also played rugby sevens for New Zealand, competing in the 2015–16 World Rugby Sevens Series and the 2016 Olympics.
Williams has boxed professionally seven times, winning all of his heavyweight bouts. He was the New Zealand Professional Boxing Association (NZPBA) Heavyweight Champion and World Boxing Association (WBA) International Heavyweight Champion, but was stripped of these titles after failing to respond to challenges.