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 1882, the townships of Usborne were added to the riding, and that of South Easthope was excluded.

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.