Colin Peter Greening (born March 9, 1986) is a Canadian former professional ice hockey left winger.

While playing for Upper Canada College in Toronto, Ontario, Greening was selected by the Ottawa Senators in the seventh round, 204th overall, of the 2005 NHL Entry Draft.

Greening played four full seasons of NCAA collegiate hockey at Cornell University without missing a single game, serving as captain in his junior and senior year and being selected for membership in the Quill and Dagger society.

On February 9, 2016, Greening was traded to the Toronto Maple Leafs in a nine-player deal which saw Dion Phaneuf going to the Ottawa Senators.

On July 1, 2017, Greening as a free agent opted to remain with the Maple Leafs, re-signing to a one-year, two-way deal.