Gregory Dewar (January 9, 1956-) is a politician in Manitoba, Canada. He is currently a member of the Manitoba legislature.

Dewar was born in Selkirk, Manitoba, the grandson of former Mayor Ben Massey . He was educated at the University of Winnipeg, and worked as a small businessman prior to entering political life. Dewar served as treasurer of the Selkirk local of the Manitoba Metis Federation , and was a founding director of the Maurepas Village Housing Cooperative. He was also involved in the Selkirk Restitution and Reconciliation Committee, a program which assists young offenders.

Dewar was first elected to the Manitoba legislature in the provincial election of 1990, running as a New Democrat in the riding of Selkirk. He received 3735 votes, against 3467 for Progressive Conservative Russ Farrell (incumbent Liberal Gwen Charles was third with 3009). Dewar was re-elected by a wider margin in the 1995 election, and by a comfortable margin in 1999. The NDP formed government following the 1999 election, and Dewar was appointed Government Whip .

Dewar supported Lorne Nystrom's bid to become leader of the federal New Democratic Party in 1995. In 2003, he supported Bill Blaikie.

Dewar was easily re-elected in the provincial election of 2003, receiving more than 60% of the vote in his riding. As of 2004, he still holds the position of Government Whip.