Colorado was admitted to the Union on August 1, 1876 and elects U.S. senators to Senate class 2 and class 3.
Both of Colorado's current U.S. senators are Democrats Michael Bennet (serving since 2009) and John Hickenlooper (serving since 2021). Colorado is one of sixteen states alongside California, Delaware, Georgia, Hawaii, Idaho, Louisiana, Maine, Massachusetts, Minnesota, Missouri, Nevada, Pennsylvania, South Dakota, Utah, and West Virginia, to have a younger senior senator and an older junior senator.
Henry M. Teller was Colorado's longest-serving senator (1876âÂÂ1882; 1885âÂÂ1909).
|- style="height:2em" | colspan=3 | Vacant | Aug 1, 1876 âÂÂ<br/>Nov 15, 1876 | Colorado did not elect its senators until three months after statehood. | rowspan=2 | 1 | rowspan=2 | rowspan=3 | 1 | Colorado did not elect its senators until three months after statehood. | Aug 1, 1876 âÂÂ<br/>Nov 15, 1876 | colspan=3 | Vacant
|- style="height:2em" ! rowspan=4 | 1 | rowspan=4 align=left | <br/>Henry M. Teller<br /> | rowspan=4 | Republican | rowspan=4 nowrap | Nov 15, 1876 âÂÂ<br/>Apr 17, 1882 | Elected in 1876. | rowspan=2 | Elected in 1876.Retired. | rowspan=2 nowrap | Nov 15, 1876 âÂÂ<br/>Mar 3, 1879 | rowspan=2 | Republican | rowspan=2 align=right | <br/>Jerome B. Chaffee<br /> ! rowspan=2 | 1
|- style="height:2em" | rowspan=3 | Elected to next term in 1876 or 1877.Resigned to become U.S. Secretary of the Interior. | rowspan=5 | 2 |
|- style="height:2em" | | rowspan=5 | 2 | rowspan=5 | Elected in 1879.Lost re-nomination. | rowspan=5 nowrap | Mar 4, 1879 âÂÂ<br/>Mar 3, 1885 | rowspan=5 | Republican | rowspan=5 align=right | <br/>Nathaniel P. Hill<br /> ! rowspan=5 | 2
|- style="height:2em" | rowspan=3
|- style="height:2em" ! 2 | align=left | <br/>George M. Chilcott<br /> | | Republican | nowrap | Apr 17, 1882 âÂÂ<br/>Jan 27, 1883 | Appointed to continue Teller's term.Did not run to finish the term.
|- style="height:2em" ! 3 | align=left | <br/>Horace Tabor<br /> | | Republican | nowrap | Jan 27, 1883 âÂÂ<br/>Mar 3, 1883 | Elected to finish Teller's term.Retired.
|- style="height:2em" ! rowspan=3 | 4 | rowspan=3 align=left | <br/>Thomas M. Bowen<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Mar 4, 1883 âÂÂ<br/>Mar 3, 1889 | rowspan=3 | Election date unknown.Unknown if retired or lost re-election. | rowspan=3 | 3 |
|- style="height:2em" | | rowspan=3 | 3 | rowspan=3 | Elected in 1885. | rowspan=12 nowrap | Mar 4, 1885 âÂÂ<br/>Mar 3, 1909 | rowspan=6 | Republican | rowspan=12 align=right | <br/>Henry M. Teller<br /> ! rowspan=12 | 3
|- style="height:2em" |
|- style="height:2em" ! rowspan=6 | 5 | rowspan=6 align=left | <br/>Edward O. Wolcott<br /> | rowspan=6 | Republican | rowspan=6 nowrap | Mar 4, 1889 âÂÂ<br/>Mar 3, 1901 | rowspan=3 | Elected in 1889. | rowspan=3 | 4 |
|- style="height:2em" | | rowspan=3 | 4 | rowspan=3 | Re-elected in 1891.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1895.Lost re-election. | rowspan=3 | 5 |
|- style="height:2em" | | rowspan=3 | 5 | rowspan=3 | Re-elected in 1897. | rowspan=3 | Silver Republican
|- style="height:2em" |
|- style="height:2em" ! rowspan=3 | 6 | rowspan=3 align=left | <br/>Thomas M. Patterson<br /> | rowspan=3 | Democratic | rowspan=3 nowrap | Mar 4, 1901 âÂÂ<br/>Mar 3, 1907 | rowspan=3 | Elected in 1901.Retired. | rowspan=3 | 6 |
|- style="height:2em" | | rowspan=3 | 6 | rowspan=3 | Re-elected in 1903.Retired. | rowspan=3 | Democratic
|- style="height:2em" |
|- style="height:2em" ! rowspan=5 | 7 | rowspan=5 align=left | <br/>Simon Guggenheim<br /> | rowspan=5 | Republican | rowspan=5 nowrap | Mar 4, 1907 âÂÂ<br/>Mar 3, 1913 | rowspan=5 | Elected in 1907.Retired. | rowspan=5 | 7 |
|- style="height:2em" | rowspan=2 | rowspan=5 | 7 | Elected in 1909.Died. | nowrap | Mar 4, 1909 âÂÂ<br/>Jan 11, 1911 | | Democratic | align=right | <br/>Charles J. Hughes Jr.<br /> ! 4
|- style="height:2em" | rowspan=2 | | rowspan=2 nowrap | Jan 11, 1911 âÂÂ<br/>Jan 15, 1913 | rowspan=2 colspan=3 | Vacant
|- style="height:2em" | rowspan=2
|- style="height:2em" | rowspan=2 | Elected to finish Hughes's term. | rowspan=5 nowrap | Jan 15, 1913 âÂÂ<br/>Mar 3, 1921 | rowspan=5 | Democratic | rowspan=5 align=right | <br/>Charles S. Thomas<br /> ! rowspan=5 | 5
|- style="height:2em" ! rowspan=3 | 8 | rowspan=3 align=left | <br/>John F. Shafroth<br /> | rowspan=3 | Democratic | rowspan=3 nowrap | Mar 4, 1913 âÂÂ<br/>Mar 3, 1919 | rowspan=3 | Elected in 1913.Lost re-election. | rowspan=3 | 8 |
|- style="height:2em" | | rowspan=3 | 8 | rowspan=3 | Re-elected in 1914.Lost re-election.
|- style="height:2em" |
|- style="height:2em" ! rowspan=9 | 9 | rowspan=9 align=left | <br/>Lawrence C. Phipps<br /> | rowspan=9 | Republican | rowspan=9 nowrap | Mar 4, 1919 âÂÂ<br/>Mar 3, 1931 | rowspan=6 | Elected in 1918. | rowspan=6 | 9 |
|- style="height:2em" | | rowspan=6 | 9 | rowspan=2 | Elected in 1920.Died. | rowspan=2 nowrap | Mar 4, 1921 âÂÂ<br/>Mar 24, 1923 | rowspan=2 | Republican | rowspan=2 align=right | <br/>Samuel D. Nicholson<br /> ! rowspan=2 | 6
|- style="height:2em" | rowspan=4
|- style="height:2em" | | nowrap | Mar 24, 1923 âÂÂ<br/>May 17, 1923 | colspan=3 | Vacant
|- style="height:2em" | Appointed to continue Nicholson's term.Retired. | nowrap | May 17, 1923 âÂÂ<br/>Nov 30, 1924 | | Democratic | align=right | <br/>Alva B. Adams<br /> ! 7
|- style="height:2em" | rowspan=2 | Elected to finish Nicholson's term.Lost renomination. | rowspan=2 nowrap | Dec 1, 1924 âÂÂ<br/>Mar 3, 1927 | rowspan=2 | Republican | rowspan=2 align=right | <br/>Rice W. Means<br /> ! rowspan=2 | 8
|- style="height:2em" | rowspan=3 | Re-elected in 1924.Retired. | rowspan=3 | 10 |
|- style="height:2em" | | rowspan=6 | 10 | rowspan=3 | Elected in 1926.Died. | rowspan=3 nowrap | Mar 4, 1927 âÂÂ<br/>Aug 27, 1932 | rowspan=3 | Republican | rowspan=3 align=right | <br/>Charles W. Waterman<br /> ! rowspan=3 | 9
|- style="height:2em" |
|- style="height:2em" ! rowspan=6 | 10 | rowspan=6 align=left | <br/>Edward P. Costigan<br /> | rowspan=6 | Democratic | rowspan=6 nowrap | Mar 4, 1931 âÂÂ<br/>Jan 3, 1937 | rowspan=6 | Elected in 1930.Retired. | rowspan=6 | 11 | rowspan=4
|- style="height:2em" | | nowrap | Aug 27, 1932 âÂÂ<br/>Sep 26, 1932 | colspan=3 | Vacant
|- style="height:2em" | Appointed to continue Waterman's term.Lost election to finish Waterman's term. | nowrap | Sep 26, 1932 âÂÂ<br/>Dec 6, 1932 | | Democratic | align=right | <br/>Walter Walker<br /> ! 10
|- style="height:2em" | Elected to finish Waterman's term.Lost election to next term. | nowrap | Dec 7, 1932 âÂÂ<br/>Mar 3, 1933 | | Republican | align=right | <br/>Karl C. Schuyler<br /> ! 11
|- style="height:2em" | | rowspan=3 | 11 | rowspan=3 | Elected in 1932. | rowspan=5 nowrap | Mar 4, 1933 âÂÂ<br/>Dec 1, 1941 | rowspan=5 | Democratic | rowspan=5 align=right | <br/>Alva B. Adams<br /> ! rowspan=5 | 12
|- style="height:2em" |
|- style="height:2em" ! rowspan=11 | 11 | rowspan=11 align=left | <br/>Edwin C. Johnson<br /> | rowspan=11 | Democratic | rowspan=11 nowrap | Jan 3, 1937 âÂÂ<br/>Jan 3, 1955 | rowspan=5 | Elected in 1936. | rowspan=5 | 12 |
|- style="height:2em" | | rowspan=5 | 12 | rowspan=2 | Re-elected in 1938.Died.
|- style="height:2em" | rowspan=3
|- style="height:2em" | | nowrap | Dec 1, 1941 âÂÂ<br/>Dec 20, 1941 | colspan=3 | Vacant
|- style="height:2em" | rowspan=2 | Appointed to continue Adams's term.Elected in 1942 to finish Adams's term. | rowspan=8 nowrap | Dec 20, 1941 âÂÂ<br/>Jan 3, 1957 | rowspan=8 | Republican | rowspan=8 align=right | <br/>Eugene Millikin<br /> ! rowspan=8 | 13
|- style="height:2em" | rowspan=3 | Re-elected in 1942. | rowspan=3 | 13 |
|- style="height:2em" | | rowspan=3 | 13 | rowspan=3 | Re-elected in 1944.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1948.Retired to run for Governor. | rowspan=3 | 14 |
|- style="height:2em" | | rowspan=3 | 14 | rowspan=3 | Re-elected in 1950.Retired
|- style="height:2em" |
|- style="height:2em" ! rowspan=9 | 12 | rowspan=9 align=left | <br/>Gordon Allott<br /> | rowspan=9 | Republican | rowspan=9 nowrap | Jan 3, 1955 âÂÂ<br/>Jan 3, 1973 | rowspan=3 | Elected in 1954. | rowspan=3 | 15 |
|- style="height:2em" | | rowspan=3 | 15 | rowspan=3 | Elected in 1956.Lost re-election. | rowspan=3 nowrap | Jan 3, 1957 âÂÂ<br/>Jan 3, 1963 | rowspan=3 | Democratic | rowspan=3 align=right | <br/>John A. Carroll<br /> ! rowspan=3 | 14
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1960. | rowspan=3 | 16 |
|- style="height:2em" | | rowspan=3 | 16 | rowspan=3 | Elected in 1962. | rowspan=6 nowrap | Jan 3, 1963 âÂÂ<br/>Jan 3, 1975 | rowspan=6 | Republican | rowspan=6 align=right | <br/>Peter H. Dominick<br /> ! rowspan=6 | 15
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1966.Lost re-election. | rowspan=3 | 17 |
|- style="height:2em" | | rowspan=3 | 17 | rowspan=3 | Re-elected in 1968.Lost re-election.
|- style="height:2em" |
|- style="height:2em" ! rowspan=3 | 13 | rowspan=3 align=left | <br/>Floyd Haskell<br /> | rowspan=3 | Democratic | rowspan=3 nowrap | Jan 3, 1973 âÂÂ<br/>Jan 3, 1979 | rowspan=3 | Elected in 1972.Lost re-election. | rowspan=3 | 18 |
|- style="height:2em" | | rowspan=3 | 18 | rowspan=3 | Elected in 1974. | rowspan=6 nowrap | Jan 3, 1975 âÂÂ<br/>Jan 3, 1987 | rowspan=6 | Democratic | rowspan=6 align=right | <br/>Gary Hart<br /> ! rowspan=6 | 16
|- style="height:2em" |
|- style="height:2em" ! rowspan=6 | 14 | rowspan=6 align=left | <br/>William L. Armstrong<br /> | rowspan=6 | Republican | rowspan=6 nowrap | Jan 3, 1979 âÂÂ<br/>Jan 3, 1991 | rowspan=3 | Elected in 1978. | rowspan=3 | 19 |
|- style="height:2em" | | rowspan=3 | 19 | rowspan=3 | Re-elected in 1980.Retired.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 1984.Retired. | rowspan=3 | 20 |
|- style="height:2em" | | rowspan=3 | 20 | rowspan=3 | Elected in 1986.Retired. | rowspan=3 nowrap | Jan 3, 1987 âÂÂ<br/>Jan 3, 1993 | rowspan=3 | Democratic | rowspan=3 align=right | <br/>Tim Wirth<br /> ! rowspan=3 | 17
|- style="height:2em" |
|- style="height:2em" ! rowspan=4 | 15 | rowspan=4 align=left | <br/>Hank Brown<br /> | rowspan=4 | Republican | rowspan=4 nowrap | Jan 3, 1991 âÂÂ<br/>Jan 3, 1997 | rowspan=4 | Elected in 1990.Retired. | rowspan=4 | 21 |
|- style="height:2em" | | rowspan=4 | 21 | rowspan=4 | Elected in 1992.Changed parties on March 3, 1995. | rowspan=7 nowrap | Jan 3, 1993 âÂÂ<br/>Jan 3, 2005 | rowspan=2 | Democratic | rowspan=7 align=right | <br/>Ben Nighthorse Campbell<br /> ! rowspan=7 | 18
|- style="height:2em" | rowspan=2
|- style="height:2em" | rowspan=5 | Republican
|- style="height:2em" ! rowspan=6 | 16 | rowspan=6 align=left | <br/>Wayne Allard<br /> | rowspan=6 | Republican | rowspan=6 nowrap | Jan 3, 1997 âÂÂ<br/>Jan 3, 2009 | rowspan=3 | Elected in 1996. | rowspan=3 | 22 |
|- style="height:2em" | | rowspan=3 | 22 | rowspan=3 | Re-elected in 1998.Retired.
|- style="height:2em" |
|- style="height:2em" | rowspan=3 | Re-elected in 2002.Retired. | rowspan=3 | 23 |
|- style="height:2em" | | rowspan=4 | 23 | rowspan=3 | Elected in 2004.Resigned to become U.S. Secretary of the Interior. | rowspan=3 nowrap | Jan 3, 2005 âÂÂ<br/>Jan 20, 2009 | rowspan=3 | Democratic | rowspan=3 align=right | <br/>Ken Salazar<br /> ! rowspan=3 | 19
|- style="height:2em" |
|- style="height:2em" ! rowspan=4 | 17 | rowspan=4 align=left | <br/>Mark Udall<br /> | rowspan=4 | Democratic | rowspan=4 nowrap | Jan 3, 2009 âÂÂ<br/>Jan 3, 2015 | rowspan=4 | Elected in 2008.Lost re-election. | rowspan=4 | 24 | rowspan=2
|- style="height:2em" | Appointed to finish Salazar's term. | rowspan=10 nowrap | Jan 21, 2009 âÂÂ<br/>present | rowspan=10 | Democratic | rowspan=10 align=right | <br/>Michael Bennet<br /> ! rowspan=10 | 20
|- style="height:2em" | | rowspan=3 | 24 | rowspan=3 | Elected to a full term in 2010.
|- style="height:2em" |
|- style="height:2em" ! rowspan=3 | 18 | rowspan=3 align=left | <br/>Cory Gardner<br /> | rowspan=3 | Republican | rowspan=3 nowrap | Jan 3, 2015 âÂÂ<br/>Jan 3, 2021 | rowspan=3 | Elected in 2014.Lost re-election. | rowspan=3 | 25 |
|- style="height:2em" | | rowspan=3 | 25 | rowspan=3 | Re-elected in 2016.
|- style="height:2em" |
|- style="height:2em" ! rowspan=3 | 19 | rowspan=3 align=left | <br/>John Hickenlooper<br /> | rowspan=3 | Democratic | rowspan=3 nowrap | Jan 3, 2021 âÂÂ<br/>present | rowspan=3 | Elected in 2020. | rowspan=3 | 26 |
|- style="height:2em" | | rowspan=3 |26 | rowspan=3 | Re-elected in 2022.
|- style="height:2em" |
|- style="height:2em" | rowspan=2 colspan=5 | To be determined in the 2026 election. | rowspan=2 | 27 |
|- style="height:2em" | | 27 | colspan=5 | To be determined in the 2028 election.