William Mark Greig (born January 25, 1970) is a Canadian former professional ice hockey right winger who played nine seasons in the National Hockey League (NHL) for the Hartford Whalers, Toronto Maple Leafs, Calgary Flames and Philadelphia Flyers.

[1] He is the younger brother of former NHL player Bruce Greig.

Greig was drafted 15th overall by the Whalers in the 1990 NHL Entry Draft and scored 13 goals and 27 assists for 40 points in 125 games during his NHL career.

Greig and his wife Cindy have three children, two daughters Kyra and Dara and one son Ridly, a centre, who was selected in the first round by the Ottawa Senators in the 2020 NHL Entry Draft.

[2] His daughter, Dara, is a professional ice hockey player for the Montreal Victoire of the Professional Women's Hockey League (PWHL).