Tim Peterson is a politician in Ontario, Canada. He is currently a member of the Legislative Assembly of Ontario, representing the Greater Toronto Area riding of Mississauga South for the Liberal Party.

Tim Peterson is the brother of former Ontario Premier David Peterson and current federal cabinet minister Jim Peterson. He was the last of the three brothers to enter political life.

Peterson has a Bachelor of Arts degree in Economics from the University of Western Ontario. He is a director of Northern Crown Capital, Inc. (a merchant banking firm) and has sat on the Board of Directors of Process Capital, Nordex Explosives and Oxegen and Prescott Paper Products, as well as the Mississauga Hospital Foundation.

In 1997, he pled guilty to the minor offense of removing a sign belonging to Peter Cobbold , a Reform Party candidate running against his brother Jim in the federal riding of Willowdale.

Despite his family's political background and a surge in Liberal support during the 2003 provincial election, Peterson was still regarded as a longshot against incumbent Progressive Conservative Margaret Marland, a longtime MPP from the region. It was a surprise to most concerned when Peterson defeated Marland by 234 votes on election night.

On October 23, 2003, Peterson was named parliamentary assistant to Jim Bradley, the Ontario Minister of Tourism and Recreation .