Matthew Guinness-King (born April 7, 1980) is a Canadian former international rugby union player.
Guinness-King, born in Woodstock, Ontario, attended Upper Canada College while growing up in Toronto.
A Balmy Beach product, Guinness-King was primarily a centre and gained 11 caps for Canada, debuting against the United States in Chicago in 2002. He made Canada's squad for the 2003 Rugby World Cup, where he played on a wing in their pool match against the All Blacks. As a rugby sevens player, Guinness-King further represented Canada at the 2005 World Cup and 2006 Commonwealth Games. He captained Cambridge University in the 2011 Varsity Match.