The Southeastern Connecticut region comprises, as the name suggests, the southeastern corner of the state of Connecticut. It is roughly contiguous with the boundaries of New London County, and is sometimes referred to as Greater New London or by the tourist slogan Mystic and More.

Southeastern Connecticut has historically been an area heavily dependent on traditional New England economic activities such as fishing, whaling, oystering, and the defense industry. In the present day, the area remains the primary home of the state's fishing and shellfish activity, but has since diversified its economic base to include tourism, gaming, and other services. Culturally, the area is heavily influenced by a mixture of its Yankee past and more recent immigrant groups, most notably Portuguese-Americans. The region can be said to be somewhat similar in this aspect to New Bedford, Massachusetts.

The area is home to the United States Coast Guard Academy in New London, a United States Navy base in Groton, the Pfizer world research headquarters, and the Mohegan Sun and Foxwoods casinos.