Perth—Middlesex was an electoral district in Ontario, Canada, that was represented in the House of Commons of Canada from 1997 to 2003 and in the Legislative Assembly of Ontario from 1999 to 2007. This riding was created in 1996 from parts of Lambton—Middlesex, London—Middlesex and Perth—Wellington—Waterloo ridings. It consisted of: * the County of Perth (including the City of Stratford and the Town of St Mary's) and * the northeast part of the County of Middlesex (consisting of the Townships of McGillivray, East Williams, Lobo, Biddulph and West Nissouri).