Mannheim 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.
In the 2021 Census of Population conducted by Statistics Canada, Mannheim had a population of 1,002 living in 330 of its 332 total private dwellings, a change of from its 2016 population of 982. With a land area of , it had a population density of in 2021.