| Post: | Ambassador |
| Body: | the United States to San Marino |
| Nativename: | Ambasciatore degli Stati Uniti d'America in San Marino |
| Insignia: | US Department of State official seal.svg |
| Insigniasize: | 120 |
| Insigniacaption: | Seal of the United States Department of State |
| Incumbent: | Jack Markell |
| Incumbentsince: | September 23, 2023 |
| Nominator: | The President of the United States |
| Inaugural: | Ronald P. Spogli as Ambassador Extraordinary and Plenipotentiary |
| Formation: | November 22, 2006 |
| Website: | United States Virtual Presence Post Republic of San Marino |
The United States ambassador to San Marino is the official representative of the government of the United States to the government of San Marino. The ambassador is concurrently the ambassador to Italy, while resident in Rome, Italy.
| Ronald P. Spogli – Political appointee | Ambassador Extraordinary and Plenipotentiary | November 22, 2006 | March 8, 2007 | February 6, 2009 | ||
| David Thorne – Political appointee | Ambassador Extraordinary and Plenipotentiary | August 17, 2009 | September 4, 2009[1] | July 30, 2013 | ||
| John R. Phillips – Political appointee | Ambassador Extraordinary and Plenipotentiary | August 16, 2013 | September 13, 2013 | January 18, 2017 | ||
| Lewis Eisenberg – Political appointee | Ambassador Extraordinary and Plenipotentiary | August 3, 2017 | October 4, 2017 | January 4, 2021 | ||
| Jack Markell – Political appointee | Ambassador Extraordinary and Plenipotentiary | July 27, 2023 | September 23, 2023 | Incumbent |