| Election Name: | 1820 Delaware gubernatorial special election |
| Country: | Delaware |
| Type: | by-election |
| Ongoing: | no |
| Previous Election: | 1819 Delaware gubernatorial election |
| Previous Year: | 1819 |
| Next Election: | 1822 Delaware gubernatorial special election |
| Next Year: | 1822 (special) |
| Election Date: | October 3, 1820 |
| Nominee1: | John Collins |
| Party1: | Democratic-Republican Party |
| Popular Vote1: | 3,970 |
| Percentage1: | 53.00% |
| Nominee2: | Jesse Green |
| Party2: | Federalist Party (United States) |
| Popular Vote2: | 3,520 |
| Percentage2: | 47.00% |
| Governor | |
| Before Election: | Jacob Stout |
| Before Party: | Federalist Party (United States) |
| After Election: | John Collins |
| After Party: | Democratic-Republican Party |
The 1820 Delaware gubernatorial special election was held on October 3, 1820. The winner of the 1819 gubernatorial election, Henry Molleston, died before assuming office, elevating State Senate Speaker Jacob Stout to the governorship and triggering an election in 1820. However, the election was not just for the remainder of Molleston's term, but instead for a full three-year term.
Jesse Green was the Federalist nominee to succeed Stout and ran against Democratic-Republican nominee John Collins. Collins defeated Green by a slim margin, becoming the first Democratic-Republican Governor of Delaware since 1810. However, Collins died in office on April 16, 1822, triggering another special election in 1822.