Massachusetts's at-large congressional seat is an obsolete construct only used during the 1792–1793 United States House of Representatives elections in Massachusetts.
In that election, one of the state's then-14 representatives to the U.S. House was elected statewide at-large.
At that time, the U.S. state of Massachusetts included the District of Maine.
Elected at-large was David Cobb, who served in the 3rd United States Congress (March 1793–March 1795).
Other than Cobb, Massachusetts has never elected a member of the U.S. House at-large.