New Brunswick is the largest of Canada's three Maritime provinces, tucked under Quebec's Gaspé Peninsula and beside the State of Maine. On the north it is bordered by the Restigouche River and the Baie des Chaleurs.

The eastern boundary is entirely coastal, consisting of the Gulf of St Lawrence and Northumberland Strait.

Chignecto Bay and the 24-kilometre (15-mile) wide Isthmus of Chignecto, which connects New Brunswick to Nova Scotia, form part of New Brunswick's southern border. The rest is the Bay of Fundy. Its tides have carved a spectacular coastline. The province is connected to Prince Edward Island by the Confederation Bridge.