- Born: November 15, 1813 at sea off Gibraltar (on British warship)
- Parents: John Thomas O’Sullivan (Irish-American diplomat and sea captain) and Mary Rowly (English gentlewoman)
- Spouse: No record found
- Children: No record found
- Died: March 24, 1895 on Staten Island, New York
- Highest Office: U.S. Minister to Portugal (1853-1857)
- Other Notable Positions: Editor and founder of United States Magazine and Democratic Review, founder of New York Morning News, journalist, lawyer
- Party Affiliation: Democratic Party
- Historical Note: Coined the term “Manifest Destiny” in 1845 to justify American territorial expansion. His phrase became the ideological foundation for westward expansion and the annexation of Texas and Oregon Territory.