| CONGRESS | SENATOR | TERM BEGAN | TERM ENDED | COMMENTS |
|---|---|---|---|---|
| Class 1 | ||||
| 1st-3rd | George Read (Pro-Admin) | Mar. 4, 1789 | Sept. 18, 17931 | Resigned |
| 3rd-6th | Henry Latimer (F) | Feb. 7, 1795 | Feb. 28, 1801 | Resigned |
| 6th-11th | Samuel White (F) | Feb. 28, 1801 | Nov. 4, 1809 | Appointed, then elected; Died |
| 11th-16th | Outerbridge Horsey (F) | Jan. 12, 1810 | Mar. 3, 1821 | |
| 17th-18th | Caesar A. Rodney (DR)2 | Jan. 24, 1822 | Jan. 29, 1823 | Resigned |
| 18th-19th | Thomas Clayton (Adams-Clay F, Adams, AJ, W)3 | Jan. 15, 1824 | Mar. 3, 1827 | |
| 20th-21st | Louis McLane (J) | Mar. 4, 1827 | Apr. 16, 1829 | Resigned |
| 21st-24th | Arnold Naudain (AJ) | Jan. 7, 1830 | Jun. 16, 1836 | Resigned |
| 24th-28th | Richard H. Bayard (AJ, W)4 | Jun. 17, 1836 | Mar. 3, 1845 | |
| 29th-30th | John M. Clayton (AJ, W, OP) | Mar. 4, 1845 | Feb. 23, 1849 | Resigned |
| 30th-31st | John Wales (W) | Feb. 23, 1849 | Mar. 3, 1851 | |
| 32nd-38th | James A. Bayard, Jr. (D) | Mar. 4, 1851 | Jan. 29, 1864 | Resigned |
| 38th-40th | George R. Riddle (D) | Feb. 2, 1864 | Mar. 29, 1867 | Died |
| 40th | James A. Bayard, Jr. (D) | Apr. 5, 1867 | Mar. 3, 1869 | Appointed, then elected |
| 41st-49th | Thomas F. Bayard, Sr. (D) | Mar. 4, 1869 | Mar. 6, 1885 | Resigned |
| 49th-55th | George Gray (D) | Mar. 18, 1885 | Mar. 3, 1899 | |
| 57th-58th | L. Heisler Ball (R)5 | Mar. 3, 1903 | Mar. 3, 1905 | |
| 59th-64th | Henry A. du Pont (R)6 | Jun. 13, 1906 | Mar. 3, 1917 | |
| 65th-67th | Josiah O. Wolcott (D) | Mar. 4, 1917 | Jul. 2, 1921 | Resigned |
| 67th | Thomas C. du Pont (R) | Jul. 7, 1921 | Nov. 7, 1922 | Appointed |
| 67th-70th | Thomas F. Bayard, Jr. (D) | Nov. 8, 1922 | Mar. 3, 1929 | |
| 71st-76th | John G. Townsend, Jr. (R) | Mar. 4, 1929 | Jan. 3, 1941 | |
| 77th-79th | James M. Tunnell (D) | Jan. 3, 1941 | Jan. 3, 1947 | |
| 80th-91st | John J. Williams (R) | Jan. 3, 1947 | Dec. 31, 1970 | Resigned |
| 91st-106th | William V. Roth, Jr. (R)7 | Jan. 1, 1971 | Jan. 3, 2001 | |
| 107th-118th | Thomas R. Carper (D) | Jan. 3, 2001 | Jan. 3, 2025 | |
| 119th- | Lisa Blunt Rochester (D) | Jan. 3, 2025 | Present | |
| Class 2 | ||||
| 1st-2nd | Richard Bassett (Anti-Admin) | Mar. 4, 1789 | Mar. 3, 1793 | |
| 3rd-5th | John Vining (Pro-Admin) | Mar. 4, 1793 | Jan. 19, 1798 | Resigned |
| 5th | Joshua Clayton (F) | Jan. 19, 1798 | Aug. 11, 1798 | Died |
| 5th-8th | William H. Wells (F) | Jan. 17, 1799 | Nov. 6, 1804 | Resigned |
| 8th-12th | James A. Bayard, Sr. (F) | Nov. 13, 1804 | Mar. 3, 1813 | Resigned |
| 13th-14th | William H. Wells (F) | May 28, 1813 | Mar. 3, 1817 | |
| 15th-19th | Nicholas Van Dyke (F, Adams-Clay F, Adams) | Mar. 4, 1817 | May 21, 1826 | Died |
| 19th | Daniel Rodney (Adams) | Nov. 8, 1826 | Jan. 12, 1827 | Appointed |
| 19th-20th | Henry M. Ridgely (J) | Jan. 12, 1827 | Mar. 3, 1829 | |
| 21st-24th | John M. Clayton (AJ, W, OP) | Mar. 4, 1829 | Dec. 29, 1836 | Resigned |
| 24th-29th | Thomas Clayton (Adams-Clay F, Adams, AJ, W) | Jan. 9, 1837 | Mar. 3, 1847 | |
| 30th-32nd | Presley Spruance (W) | Mar. 4, 1847 | Mar. 3, 1853 | |
| 33rd-34th | John M. Clayton (AJ, W, OP) | Mar. 4, 1853 | Nov. 9, 1856 | Died |
| 34th | Joseph P. Comegys (OP) | Nov. 19, 1856 | Jan. 14, 1857 | Appointed |
| 34th-35th | Martin W. Bates (D) | Jan. 14, 1857 | Mar. 3, 1859 | |
| 36th-41st | Willard Saulsbury, Sr. (D) | Mar. 4, 1859 | Mar. 3, 1871 | |
| 42nd-50th | Eli Saulsbury (D) | Mar. 4, 1871 | Mar. 3, 1889 | |
| 51st-53rd | Anthony Higgins (R) | Mar. 4, 1889 | Mar. 3, 1895 | |
| 54th-56th | Richard R. Kenney (D) | Jan. 19, 18978 | Mar. 3, 1901 | |
| 57th-59th | J. Frank Allee (R) | Mar. 3, 19039 | Mar. 3, 1907 | |
| 63rd-65th | Willard Saulsbury, Jr. (D) | Mar. 4, 1913 | Mar. 3, 1919 | |
| 66th-68th | L. Heisler Ball (R) | Mar. 4, 1919 | Mar. 3, 1925 | |
| 69th-68th | Thomas C. du Pont (R) | Mar. 4, 1925 | Dec. 9, 1928 | Resigned |
| 70th-74th | Daniel O. Hastings (R) | Dec. 10, 1928 | Jan. 3, 1937 | Appointed, then elected |
| 75th-77th | James H. Hughes (D) | Jan. 3, 1937 | Jan. 3, 1943 | |
| 78th-80th | C. Douglass Buck (R) | Jan. 3, 1943 | Jan. 3, 1949 | |
| 81st-86th | Joseph A. Frear, Jr. (D) | Jan. 3, 1949 | Jan. 3, 1961 | |
| 87th-92nd | J. Caleb Boggs (R) | Jan. 3, 1961 | Jan. 3, 1973 | |
| 93rd-111th | Joseph R. Biden, Jr. (D) | Jan. 3, 1973 | Jan. 15, 2009 | Resigned |
| 111th | Ted Kaufman (D) | Jan. 15, 2009 | Nov. 15, 2010 | Appointed |
| 111th- | Christopher A. Coons (D) | Nov. 15, 2010 | Present | |
1. Vacancy from Sept. 18, 1793, to Feb. 7, 1795. Kensey Johns was appointed by governor Mar. 19, 1794, to fill vacancy, but by Senate resolution of Mar. 28, 1794, was declared not entitled to a seat.
2. Elected to fill vacancy in term commencing Mar. 4, 1821, and took his seat Jan. 24, 1822; vacancy in this class from Mar. 4, 1821, to Jan. 23, 1822.
3. Vacancy from Jan. 29, 1823, to Jan. 14, 1824, because of failure of legislature to elect.
4. Resigned Sept. 19, 1839 to become chief justice of Delaware, leaving seat vacant. Reelected, serving from Jan. 12, 1841, to Mar. 3, 1845. Vacancy from Sept. 19, 1839, to Jan. 11, 1841.
5. Vacancy from Mar. 4, 1899, to Mar. 2, 1903, because of failure of legislature to elect.
6. Vacancy from Mar. 4, 1905, to June 13, 1906, because of failure of legislature to elect.
7. Elected for the term commencing January 3, 1971; subsequently appointed January 1, 1971, to fill the vacancy caused by the resignation of John J. Williams for the term ending January 3, 1971.
8. Vacancy from Mar. 4, 1895, to Jan. 19, 1897, because of failure of legislature to elect.
9. Vacancy from Mar. 4, 1901, to Mar. 2, 1903, because of failure of legislature to elect.
