Placentia, Newfoundland and Labrador in the context of "Terre-Neuve (New France)"

St. Mary's Bay is one of many bays in Newfoundland, Canada, where bay is taken as a regional subdivision, somewhat along the lines of county divisions (Newfoundland, a largely maritime society, lacks counties). It is the most southern and eastern of Newfoundland's major bays.

It is located on the southern shore of the Avalon Peninsula and is the heartland of the Irish Newfoundlanders, who live all along its shores, stretching west to the Cape Shore and Placentia and northeast to the Southern Shore and St. John's. Like most Irish Newfoundlanders, area residents trace their ancestry to County Waterford, County Wexford, County Kilkenny, south County Tipperary and east County Cork. In addition to being Irish, the region is also overwhelmingly Roman Catholic.

Placentia Bay (French: Baie de Plaisance) is a body of water on the southeast coast of Newfoundland, Canada. It is formed by Burin Peninsula on the west and Avalon Peninsula on the east. Fishing grounds in the bay were used by native people long before the first European fishermen arrived in the 16th century. For a time, the French controlled the bay. They built their capital at Placentia on the east coast. The British gained Placentia during the Treaty of Utrecht in 1713. The town and nearby Castle Hill are national historic sites. English settlement followed in the bay and today the main communities are Burin, Marystown, and Placentia.

On 14 August 1941 US Naval Station Argentia located in Little Placentia Sound was the site of the Atlantic Conference for the Atlantic Charter, where Winston Churchill and Franklin D. Roosevelt met face to face for the first time since both took office and the start of World War II.