Perth South is a township in southwestern Ontario, Canada, at the confluence of the River Thames and the Avon River in the County of Perth.
Canada's ninth Prime Minister, Arthur Meighen, was born in Anderson, a community in Perth South.
The township encompasses the communities of Anderson, Avonbank, Avonton, Conroy, Flannigan Corners, Harmony, Metropolitan, Rannoch, Science Hill, Sebringville and St. Pauls Station.
According to the 2011 Statistics Canada Census:
- Population: 3,993
- % Change (2001-2006): -3.4
- Area (km².): 393.03
- Density (persons per km².): 10.2
- Private dwellings occupied by usual residents: 1393 (total dwellings: 1456)
- Population in 2011: 3993
- Population in 2006: 4132
- Population in 2001: 4304 (or 4299 when adjusted for 2006 boundaries)
- Population in 1996: 4343