The headland of Cape St. Mary's is located at the southern tip of the south-western arm of the Avalon Peninsula of the island of Newfoundland in the Canadian province of Newfoundland and Labrador.
Cape St. Mary's is probably one of the most well known capes of the province, it has been written in song and history. There is a well known folk song about the Cape called "Let Me Fish Off Cape St. Mary's" by Otto P. Kelland.
The Cape St. Mary's Ecological Reserve is a wildlife reserve located east of the Cape.