Matchedash Bay is a bay and Ramsar wetland in Simcoe County in Central Ontario, Canada. It is the "final inland extension of Severn Sound" on Lake Huron's Georgian Bay, and is "situated at the interface between the Saint Lawrence Lowlands and the Canadian Shield ". It exhibits geologically unique features at the junction of the Canadian Shield and southern Ontario limestone. Wetland habitats in Matchedash Bay are varied, and include swamps, fens, cattail marshes, wet meadows and beaver ponds. Other features include "permanent freshwater lakes; upland hardwood forest, agricultural lands, native grass meadows and a unique, coniferous wetland forest".