Perth County is a county in the Canadian province of Ontario in Southwestern Ontario, 100 kilometres (62 mi) west of Toronto. Its population centres are Listowel, Mitchell and Milverton. The City of Stratford and the Town of St. Marys are within the Perth census division, but are separate from Perth County. The 2016 population of Perth County was 38,066.

Stratford is a city on the Avon River within Perth County in southwestern Ontario, Canada, with a 2021 population of 33,232 in a land area of 30.02 square kilometres (11.59 sq mi). Stratford is the seat of Perth County, which was settled by English, Irish, Scottish and German immigrants, in almost equal numbers, starting in the 1820s but primarily in the 1830s and 1840s. Most became farmers; even today, the area around Stratford is known for mixed farming, dairying and hog production.