This is a complete list of United States senators during the 76th United States Congress listed by seniority from January 3, 1939, to January 3, 1941.
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 1940 election) are listed at the end of the list with no number.
In this Congress, the most senior junior senator was Gerald Nye. The distinction of most junior senior senator was held by three different individuals: William Smathers from the start of the 76th Congress until April 9, 1939; Scott Lucas from April 9, 1939 to January 19, 1940; and D. Worth Clark from January 19, 1940 to the end of the 76th Congress.
The senior senators by class were Henry F. Ashurst (R-Arizona) from Class 1, William Borah (R-Idaho) from Class 2, and Ellison D. Smith (D-South Carolina) from Class 3. Borah died on January 19, 1940 with Morris Sheppard (D-Texas) became the senior senator from his class.