Renfrew South was a federal riding represented in the House of Commons of Canada from 1867 to 1968. It was located in the province of Ontario. The federal riding was created by the British North America Act of 1867 and was abolished in 1966, with the riding being apportioned into Frontenac—Lennox and Addington, Lanark and Renfrew, and Renfrew North.
The South Riding initially consisted of the Townships of McNab, Bagot, Blithfield, Brougham, Horton, Adamston, Grattan, Matawatchan, Griffith, Lyndoch, Raglan, Radcliffe, Brudenell, Sebastopol, and the Villages of Arnprior and Renfrew.
In 1872, the Townships of Hagarty, Richards, Sherwood, Burns and Renfrew, Jones, were added to the South Riding.
In 1892, the part of the village of Eganville south of the River Bonnechère was added to the riding.
In 1924, "Renfrew South" was defined to consist of the part of the county of Renfrew lying south of and including the townships of Richards, Haggarty, Brudenell, Sebastopol, Grattan, Admaston and Horton, and including the part of the village of Eganville that lies in the township of Grattan.
In 1952, it was defined to consist of the part of the county of Renfrew lying south and west of and including the townships of Richards, Hagarty, Algoma South, Grattan, Admaston and Horton, the part of the village of Eganville lying within the township of Grattan, and, in the territorial district of Nipissing, the townships of Airy, Murchison, Dickens, Sabine, and Lyell.
The electoral district was abolished in 1966 when it was redistributed between Frontenac—Lennox and Addington, Lanark and Renfrew and Renfrew North ridings.
This riding elected the following members of the House of Commons of Canada: