William Dagger (born 21 February 1999) is an English professional rugby league footballer who plays as a fullback or on the wing for Hull Kingston Rovers in the Betfred Super League. He has previously played for the Warrington Wolves in the Super League. Dagger has spent time on loan from Hull KR at the York City Knights in Betfred League 1, and at the Leigh Centurions and Featherstone Rovers in the Betfred Championship.