Petersburg is an unincorporated community in Wilmot Township in the Regional Municipality of Waterloo, Ontario, Canada.

It is recognized as a designated place by Statistics Canada.

The village was settled and named afer Peter Wilker, a native of Hesse-Darmstadt, Germany in the 1830's.

[1] The locality had a school in 1842, a post office in 1849 amd in 1856, the locality was a station on the Grand Trunk Railway.

[2] In the 2021 Census of Population conducted by Statistics Canada, Petersburg had a population of 374 living in 147 of its 149 total private dwellings, a change of 10% from its 2016 population of 340.