Ontario South was a federal electoral district represented in the House of Commons of Canada from 1867 to 1925.

It was created by the British North America Act of 1867.

In 1882, the Township of Reach and the village of Port Perry were added to the riding.

The electoral district was abolished in 1924 when it was merged into Ontario riding.

Note: Newspaper for the time recorded the name of Gibbs' opponent as Truman P.