John Powell (June 19, 1809 – February 24, 1881) was a Canadian politician who served as mayor of Toronto and played an important role in the Upper Canada Rebellion. Powell was a member of the "Family Compact," the small group of elite families that controlled the politics of Upper Canada in the first half of the nineteenth century. His father, Captain John Powell, was the son-in-law of General Æneas Shaw and his grandfather was Chief Justice William Dummer Powell.
A lawyer by training, in the 1837 elections Powell was elected alderman for St. Andrew's Ward, which then covered the area between King and Queen Streets west of Yonge and east of Bathurst. When former mayor William Lyon Mackenzie attempted to foment a rebellion against the Compact and Governor Sir Francis Bond Head, Powell became an important member of the forces opposing him.
On the night of December 4 Powell and companion Archibald Macdonald left the central part of town to investigate the reports of rebel activities to the north. Unbeknownst to them the rebels had captured a local armoury and were based at Montgomery's Tavern, preparing to march south.