| 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 Lattimer (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. Rodney2 (R) | Jan. 24, 1822 | Jan. 29, 1823 | Resigned |
| 18th-19th | Thomas Clayton3 (ADAMS-CLAY F, ADAMS) | 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. Bayard4 (AJ, W) | Jun. 17, 1836 | Mar. 3, 1845 | |
| 29th-30th | John M. Clayton (W) | 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) | Jan. 29, 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 Ball5 (R) | Mar. 3, 1903 | Mar. 3, 1905 | |
| 59th-64th | Henry A. du Pont6 (R) | Jun. 13, 1906 | Mar. 3, 1917 | |
| 65th-67th | Josiah O. Wolcott (D) | Mar. 4, 1917 | Jul. 2, 1921 | Resigned |
| 67th | T. Coleman du Pont (R) | Jul. 7, 1921 | Nov. 6, 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. Willliams (R) | Jan. 3, 1947 | Dec. 31, 1970 | Resigned |
| 91st-106th | William V. Roth Jr.7 (R) | Jan. 1, 1971 | Jan. 3, 2001 | |
| 107th- | Thomas R. Carper (D) | Jan. 3, 2001 | Present | |
| Class 2 | ||||
| 1st-2nd | Richard Bassett (ANTI-ADMIN, PRO-ADMIN) | Mar. 4, 1789 | Mar. 3, 1793 | |
| 3rd-5th | John Vining (PRO-ADMIN, F) | 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 VanDyke (F, ADAMS CLAY, 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) | Mar. 4, 1829 | Dec. 29, 1836 | Resigned |
| 24th-29th | Thomas Clayton (AJ, W) | Jan. 9, 1837 | Mar. 3, 1847 | |
| 30th-32nd | Presley Spruance (W) | Mar. 4, 1847 | Mar. 3, 1853 | |
| 33rd-34th | John M. Clayton (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 | James F. 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 | T. Coleman 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 | J. Allen 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 | Edward E. Kaufman Jr. (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.
