Rex Barnes (born June 4, 1959 in Grand Falls-Windsor, Newfoundland and Labrador) is a Canadian politician.

Barnes was a member of the Progressive Conservative caucus in the Canadian House of Commons, representing the riding of Gander--Grand Falls since 2002 when he was elected in a by-election. He lost his seat in the 2004 election to Liberal candidate Scott Simms.

Barnes has been a paramedic, and a volunteer worker. Barnes was the Progressive Conservative critic for Public Works and Government Services, and Transport. He served as a city councillor in Grand Falls-Windsor for 9 years.