Perth South was a federal electoral district represented in the House of Commons of Canada from 1867 to 1935.

It was created by the British North America Act of 1867, which divided the County of Perth into two ridings.

In 1903, Usborne was removed from the riding, and Easthope South and Logan townships were added.

In 1914, the part of the village of Tavistock situated in the township of Easthope South was added.

That part of Tavistock lying in the township of Easthope South was also included.