This is a complete list of United States senators during the 77th United States Congress listed by seniority from January 3, 1941, to January 3, 1943.
Order of service is based on the commencement of the senator's first term. Behind this is former service as a senator (only giving the senator seniority within their new incoming class), service as vice president, a House member, a cabinet secretary, or a governor of a state. The final factor is the population of the senator's state.
Senators who were sworn in during the middle of the Congress (up until the last senator who was not sworn in early after winning the November 1942 election) are listed at the end of the list with no number.
In this Congress, Tom Connally was the most senior junior senator. The most junior senior senator was Robert Taft until January 12, 1941, after which Harley Kilgore became the most junior senior senator.
The most senior senators by class were Kenneth McKellar (D-Tennessee) from Class 1, Morris Sheppard (D-Texas) from Class 2, and Ellison D. Smith (D-South Carolina) from Class 3.