Vermilion Bay is a bay

Bay

A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...

 in southern Louisiana

Louisiana

Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

.

Vermilion Bay is located in southwestern Iberia Parish

Iberia Parish, Louisiana

Iberia Parish is a parish located in the U.S. state of Louisiana. The parish seat is New Iberia. As of 2000, the population was 73,266.Iberia Parish is part of the New Iberia Micropolitan Statistical Area as well as the Lafayette–Acadiana Combined Statistical Area.Iberia, along with...

 and southeastern Vermilion Parish

Vermilion Parish, Louisiana

Vermilion Parish is a parish located in the U.S. state of Louisiana. The parish seat is Abbeville. As of the 2010 census, the population was 57,999....

. It is an inlet

Inlet

An inlet is a narrow body of water between islands or leading inland from a larger body of water, often leading to an enclosed body of water, such as a sound, bay, lagoon or marsh. In sea coasts an inlet usually refers to the actual connection between a bay and the ocean and is often called an...

 of the Gulf of Mexico

Gulf of Mexico

The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...

, to which it is connected to the south by a narrow strait

Strait

A strait or straits is a narrow, typically navigable channel of water that connects two larger, navigable bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not...

 called Southwest Pass

Southwest Pass (Vermilion Parish)

Southwest Pass is a narrow strait in Vermilion Parish in southern Louisiana in the United States. It connects the Gulf of Mexico to its south with Vermilion Bay to its north...

; Marsh Island

Marsh Island (Louisiana)

Marsh Island is an island off the coast of southern Louisiana in the United States.Marsh Island is an uninhabited low-lying marshy island in Iberia Parish, south coastal Louisiana, lying between Vermilion Bay and the Gulf of Mexico...

 and a portion of the Louisiana mainland in southeastern Vermilion Parish otherwise separate it from the Gulf of Mexico. On the east, Vermilion Bay connects directly to West Cote Blanche Bay.