The Belle Isle Marsh Reservation is a state park and recreation area in Boston, Massachusetts. It is best noted for being home to the last remaining salt marsh located within the city of Boston.

Located in what was once known as the Hog?s Island and the Breeds Island, the Belle Isle Marsh Reservation used to be an actual island. It has evolved through the years and is now a complete salt marsh that is home to various species of plants, shellfish, and fish, which is totally rare in a metropolitan locale.

Visitors of the Belle Isle Marsh Reservation can be best enjoyed through passive recreation like walking, jogging, birding, and dog walking. Nature observation is also a very popular use of the park.