| CONGRESS | SENATOR | TERM BEGAN | TERM ENDED | COMMENTS |
|---|---|---|---|---|
| Class 1 | ||||
| 51st-52nd | Wilbur F. Sanders (R) | Jan. 1, 1890 | Mar. 3, 1893 | |
| 53rd-55th | Lee Mantle (R, SR) | Jan. 16, 18951 | Mar. 3, 1899 | |
| 56th | William A. Clark (D) | Mar. 4, 1899 | May 15, 19002 | Resigned |
| 57th-58th | Paris Gibson (D) | Mar. 7, 1901 | Mar. 3, 1905 | |
| 59th-61st | Thomas H. Carter (R) | Mar. 4, 1905 | Mar. 3, 1911 | |
| 62nd-67th | Henry L. Myers (D) | Mar. 4, 1911 | Mar. 3, 1923 | |
| 68th-79th | Burton K. Wheeler (D) | Mar. 4, 1923 | Jan. 3, 1947 | |
| 80th-82nd | Zales N. Ecton (R) | Jan. 3, 1947 | Jan. 3, 1953 | |
| 83rd-94th | Michael J. Mansfield (D) | Jan. 3, 1953 | Jan. 3, 1977 | |
| 95th-100th | John Melcher (D) | Jan. 3, 1977 | Jan. 3, 1989 | |
| 101st-109th | Conrad Burns (R) | Jan. 3, 1989 | Jan. 3, 2007 | |
| 110th- | Jon Tester (D) | Jan. 3, 2007 | Present | |
| Class 2 | ||||
| 51st-53rd | Thomas C. Power (R) | Jan. 2, 1890 | Mar. 3, 1895 | |
| 54th-56th | Thomas H. Carter (R) | Mar. 4, 1895 | Mar. 3, 1901 | |
| 57th-59th | William A. Clark (D) | Mar. 4, 1901 | Mar. 3, 1907 | |
| 60th-62nd | Joseph M. Dixon (R) | Mar. 4, 1907 | Mar. 3, 1913 | |
| 63rd-72nd | Thomas J. Walsh (D) | Mar. 4, 1913 | Mar. 2, 1933 | Died |
| 73rd | John E. Erickson (D) | Mar. 13, 1933 | Nov. 6, 1934 | Appointed |
| 73rd-86th | James E. Murray (D) | Nov. 7, 1934 | Jan. 3, 1961 | |
| 87th-95th | Lee W. Metcalf (D) | Jan. 3, 1961 | Jan. 12, 1978 | Died |
| 95th | Paul G. Hatfield (D) | Jan. 22, 1978 | Dec. 14, 1978 | Appointed; resigned |
| 95th-113th | Max S. Baucus (D) | Dec. 15, 19783 | Feb. 6, 2014 | Resigned |
| 113th | John Walsh (D) | Feb. 9, 20144 | Jan. 3, 2015 | Appointed |
| 114th- | Steve Daines (R) | Jan. 3, 2015 | Present | |
1. Initially appointed but not seated. Vacancy from Mar. 4, 1893 to Jan.15, 1895 due to failure of legislature to elect.
2. Resigned before resolution declaring his election void due to fraud could be adopted.
3. Elected to the term beginning Jan. 3, 1979 and subsequently appointed to the remainder of the term ending Jan. 3, 1979.
4. Appointed on Febraury 9, 2014. Took the oath of office and was seated February 11, 2014.
