| CONGRESS | SENATOR | TERM BEGAN | TERM ENDED | COMMENTS |
|---|---|---|---|---|
| Class 1 | ||||
| 51st-52nd | Francis E. Warren (R) | Nov. 24, 1890 | Mar. 3, 1893 | |
| 53rd-64th | Clarence D. Clark (R) | Jan. 23, 18951 | Mar. 3, 1917 | |
| 65th-73rd | John B. Kendrick (D) | Mar. 4, 1917 | Nov. 3, 1933 | Died |
| 73rd-82nd | Joseph C. O'Mahoney (D) | Jan. 1, 1934 | Jan. 3, 1953 | Appointed, then elected |
| 83rd-85th | Frank A. Barrett (R) | Jan. 3, 1953 | Jan. 3, 1959 | |
| 86th-94th | Gale W. McGee (D) | Jan. 3, 1959 | Jan. 3, 1977 | |
| 95th-103rd | Malcolm Wallop (R) | Jan. 3, 1977 | Jan. 3, 1995 | |
| 104th-110th | Craig L. Thomas (R) | Jan. 3, 1995 | Jun. 4, 2007 | Died |
| 110th- | John Barrasso (R) | Jun. 22, 2007 | Present | Appointed, then elected |
| Class 2 | ||||
| 51st-52nd | Joseph M. Carey (R) | Nov. 15, 1890 | Mar. 3, 1895 | |
| 53rd-71st | Francis E. Warren (R) | Mar. 4, 1895 | Nov. 24, 1929 | Died |
| 71st | Patrick J. Sullivan (R) | Dec. 5, 1929 | Nov. 30, 1930 | Appointed |
| 71st-74th | Robert D. Carey (R) | Dec. 1, 1930 | Jan. 3, 1937 | |
| 75th-77th | Henry H. (Harry) Schwartz (D) | Jan. 3, 1937 | Jan. 3, 1943 | |
| 78th-80th | Edward V. Robertson (R) | Jan. 3, 1943 | Jan. 3, 1949 | |
| 81st-83rd | Lester C. Hunt (D) | Jan. 3, 1949 | Jun. 19, 1954 | Died |
| 83rd | Edward D. Crippa (R) | Jun. 24, 1954 | Nov. 28, 1954 | Appointed |
| 83rd-86th | Joseph C. O'Mahoney (D) | Nov. 29, 1954 | Jan. 3, 1961 | |
| 87th | John Joseph Hickey (D) | Jan. 3, 19612 | Nov. 6, 1962 | Appointed |
| 87th-89th | Milward L. Simpson (R) | Nov. 7, 1962 | Jan. 3, 1967 | |
| 90th-95th | Clifford P. Hansen (R) | Jan. 3, 1967 | Dec. 31, 1978 | Resigned |
| 95th-104th | Alan K. Simpson (R) | Jan. 1, 19793 | Jan. 3, 1997 | |
| 105th-116th | Michael B. Enzi (R) | Jan. 3, 1997 | Jan. 3, 2021 | |
| 117th- | Cynthia M Lummis (R) | Jan. 3, 2021 | Present | |
1. Vacancy from Mar. 4, 1893 to Jan. 22, 1895 due to failure of the legislature to elect. Asahel C. Beckwith was appointed by the governor and presented his credentials to the Senate on Mar. 15, 1893, but he did not qualify. He resigned on July 11, 1893.
2. Appointed to fill the vacancy caused by the death of Senator-elect Keith Thomson.
3. Appointed to complete term expiring Jan. 3, 1979 having been elected to term being Jan. 3, 1979.
