Missisquoi Bay is a large extension in the northern part of Lake Champlain, at the East of the output of the latter in Richelieu River.

The river of the same name flows into the bay and the Missisquoi National Wildlife Refuge is located on the American side.

It appears officially in the eighteenth century in the concession document made on April 6, 1733 to Paul-Louis de Lusignan Dazemard as the "Missiskouy Bay".

At the opening of the new bridge on the US side, the old road causeway was partly demolished which brought a flow of fresh water from Lake Champlain.

The bay has a great diversity of fauna and flora, including many species of birds, hence the establishment of a national refuge on the US side.