This is a complete list of United States senators during the 96th United States Congress listed by seniority from January 3, 1979, to January 3, 1981.
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.
In this congress, Henry M. Jackson was the most senior junior senator and Donald W. Stewart was the most junior senior senator until May 7, 1980 when Edmund Muskie resigned to become Secretary of State. William Cohen was the most junior senior senator from that date until John Durkin resigned on December 29, 1980, after which it was Gordon Humphrey.
Senators who were sworn in during the middle of the two-year congressional term (up until the last senator who was not sworn in early after winning the November 1980 election) are listed at the end of the list with no number.
The most senior senators by class were John C. Stennis (D-Mississippi) from Class 1, Strom Thurmond (R-South Carolina) from Class 2, and Warren G. Magnuson (D-Washington) from Class 3.