A geographic area of the ocean designed to protect and conserve aquatic life, habitat, and cultural resources.  In the United States, there are over 1,600 MPAs in existence, which span a range of habitats, including the open ocean, coastal areas, inter-tidal zones, and estuaries. The characteristics of a MPA commonly include conservation focus, level of protection, permanence of protection, constancy of protection, and ecological scale of protection.

The activities allowed within an MPA can vary greatly. For example, a marine reserve will typically have a “no take” restriction, meaning that no fishing or other types of resource gathering are allowed within its bounds. Other types of MPAs allow multiple uses within guidelines, such as fishing, gathering, and certain recreation activities.