Colchester is a community and unincorporated place in Southwestern Ontario, the southernmost settlement on mainland Canada, and the southernmost point with the exception of Point Pelee National Park. It is located on the north shore of Lake Erie, approximately 6 kilometres (3.7 mi) south of the town of Harrow. Colchester was formerly part of the Township of Colchester South and is now a part of the amalgamated Town of Essex within the County of Essex. Colchester shares its postal code with Harrow as N0R 1G0.

Essex is a town with a population of 21,216 in Essex County in southwestern Ontario, Canada, whose municipal borders extend to Lake Erie. Essex is also the name of the largest community within the municipality.