Robert C. Byrd served in the US Senate for 51 years, 5 months and 26 days, the longest of any senator. Daniel Inouye (49 years, 11 months) and Patrick Leahy (48 years) follow. The table lists the 25 longest tenures on Senate.gov’s own list.
Pictured: Robert C. Byrd, #1 with 51 years, 5 months and 26 days of Senate service.
| Rank | Senator | State | Dates of service | Length of service | Status | Start of service |
|---|---|---|---|---|---|---|
| 1 | Robert C. Byrd | West Virginia | Jan 3, 1959–Jun 28, 2010 | 51 years, 5 months, 26 days | Left office | 1950–1999 |
| 2 | Daniel K. Inouye | Hawaii | Jan 3, 1963–Dec 17, 2012 | 49 years, 11 months, 15 days | Left office | 1950–1999 |
| 3 | Patrick J. Leahy | Vermont | Jan 3, 1975–Jan 3, 2023 | 48 years | Left office | 1950–1999 |
| 4 | Strom Thurmond | South Carolina | Dec 14, 1954–Apr 4, 1956 and Nov 7, 1956–Jan 3, 2003 | 47 years, 5 months, 8 days | Left office | 1950–1999 |
| 5 | Edward M. Kennedy (Ted) | Massachusetts | Nov 7, 1962–Aug 25, 2009 | 46 years, 9 months, 19 days | Left office | 1950–1999 |
| 6 | Chuck Grassley | Iowa | Jan 3, 1981–present | 45 years, 10 months, 3 days (as of Nov 6, 2026) | Serving as of Nov 6, 2026 | 1950–1999 |
| 7 | Orrin G. Hatch | Utah | Jan 3, 1977–Jan 3, 2019 | 42 years | Left office | 1950–1999 |
| 8 | Mitch McConnell | Kentucky | Jan 3, 1985–present | 41 years, 10 months, 3 days (as of Nov 6, 2026) | Serving as of Nov 6, 2026 | 1950–1999 |
| 9 | Carl T. Hayden | Arizona | Mar 4, 1927–Jan 3, 1969 | 41 years, 10 months | Left office | Before 1950 |
| 10 | John C. Stennis | Mississippi | Nov 5, 1947–Jan 3, 1989 | 41 years, 1 month, 29 days | Left office | Before 1950 |
| 11 | Ted Stevens | Alaska | Dec 24, 1968–Jan 3, 2009 | 40 years, 10 days | Left office | 1950–1999 |
| 12 | William T. Cochran (Thad) | Mississippi | Dec 27, 1978–Apr 1, 2018 | 39 years, 3 months, 6 days | Left office | 1950–1999 |
| 13 | Ernest F. Hollings (Fritz) | South Carolina | Nov 9, 1966–Jan 3, 2005 | 38 years, 1 month, 25 days | Left office | 1950–1999 |
| 14 | Richard B. Russell, Jr. | Georgia | Jan 12, 1933–Jan 21, 1971 | 38 years, 10 days | Left office | Before 1950 |
| 15 | Russell B. Long | Louisiana | Dec 31, 1948–Jan 3, 1987 | 38 years, 3 days | Left office | Before 1950 |
| 16 | Francis E. Warren | Wyoming | Nov 18, 1890–Mar 3, 1893 and Mar 4, 1895–Nov 24, 1929 | 37 years, 4 days | Left office | Before 1950 |
| 17 | James O. Eastland | Mississippi | Jun 30, 1941–Sep 28, 1941 and Jan 3, 1943–Dec 27, 1978 | 36 years, 2 months, 24 days | Left office | Before 1950 |
| 18 | Warren G. Magnuson | Washington | Dec 14, 1944–Jan 3, 1981 | 36 years, 20 days | Left office | Before 1950 |
| 19 | Joseph R. Biden, Jr. | Delaware | Jan 3, 1973–Jan 15, 2009 | 36 years, 13 days | Left office | 1950–1999 |
| 20 | Pete V. Domenici | New Mexico | Jan 3, 1973–Jan 3, 2009 | 36 years | Left office | 1950–1999 |
| 20 | Carl M. Levin | Michigan | Jan 3, 1979–Jan 3, 2015 | 36 years | Left office | 1950–1999 |
| 20 | Richard G. Lugar | Indiana | Jan 3, 1977–Jan 3, 2013 | 36 years | Left office | 1950–1999 |
| 20 | Claiborne Pell | Rhode Island | Jan 3, 1961–Jan 3, 1997 | 36 years | Left office | 1950–1999 |
| 20 | Richard C. Shelby | Alabama | Jan 3, 1987–Jan 3, 2023 | 36 years | Left office | 1950–1999 |
| 25 | Kenneth D. McKellar | Tennessee | Mar 4, 1917–Jan 3, 1953 | 35 years, 10 months | Left office | Before 1950 |
No matching rows.
Source: Senate.gov’s “Longest-Serving Senators” list (as of January 22, 2025), the single source for every row. Lengths for the two senators still serving are counted to November 6, 2026 and may change when new terms begin in January 2027; the ranking does not report any election result. Senators with equal length share a rank. No senator who began serving in 2000 or later is on the list, so the filter has two start periods. This is a different ranking from the longest-serving world leaders and the longest-reigning monarchs: it covers legislators of one chamber, measured by total time in office, including gaps between stretches of service.[1][9]
Byrd, of West Virginia, served from January 3, 1959, to June 28, 2010, the longest Senate tenure in history.[1] He passed Strom Thurmond’s record on June 12, 2006.[2] In November 2009 he also passed Carl Hayden’s record for the longest service in Congress as a whole.[3] The video is a C-SPAN excerpt of a 2005 interview.[4]
Inouye represented Hawaii from January 3, 1963, to December 17, 2012.[1] He chaired the Senate Select Committee that held the 1987 Iran-Contra hearings, the subject of the video.[5]
Leahy, of Vermont, served exactly 48 years, from January 3, 1975, to January 3, 2023, the third-longest tenure on Senate.gov’s list.[1] He gave his farewell address on the Senate floor on December 20, 2022, which the video shows.[6]
Thurmond’s service of 47 years, 5 months and 8 days was in two stretches: December 1954 to April 1956, and November 1956 to January 2003.[1] The video is a 1997 news clip on him becoming the longest-serving senator to that date, and he turned 100 in December 2002, the first sitting senator to do so.[2][7]
Kennedy served Massachusetts from November 7, 1962, to August 25, 2009.[1] Senate history pages note that in 2002 three incumbents had served 40 or more years: Thurmond, Byrd and Kennedy.[8] The video is a retrospective of his career.
Grassley, of Iowa, has served since January 3, 1981.[1] Senate.gov listed his service as 44 years and 19 days on January 22, 2025; his length here is counted forward to November 6, 2026, and will change as service continues, including when new terms begin in January 2027.[9]
Hatch served Utah for exactly 42 years, from January 3, 1977, to January 3, 2019.[1] The video is his farewell floor speech, in which he was described as the longest-serving Republican senator at the time.[10]
McConnell, of Kentucky, has served since January 3, 1985.[1] Senate.gov listed 40 years and 19 days on January 22, 2025; the length here is counted to November 6, 2026 and may change when new terms begin in January 2027.[9] The video covers his record as the longest-serving Senate party leader.[11]
Hayden served Arizona from March 4, 1927, to January 3, 1969.[1] He had earlier been Arizona’s first member of the House, and his combined service in both chambers was the congressional record until Byrd passed it in 2009.[3] No verified video was found for this entry, so it shows an illustration.
Stennis served Mississippi from November 5, 1947, to January 3, 1989.[1] A tribute video describes him as the second-longest-serving senator when he retired, a ranking since passed by several others.[12]