John Louis O'Sullivan (November 15, 1813 – March 24, 1895) was an American columnist, editor, and diplomat who coined the term "manifest destiny" in 1845 to promote the annexation of Texas and the Oregon Country to the United States.

[1] O'Sullivan was an influential political writer and advocate for the Democratic Party at that time and served as U.S. minister to Portugal during the administration of President Franklin Pierce (1853–1857).

It published some of the most prominent American writers, including Nathaniel Hawthorne, Ralph Waldo Emerson, Henry David Thoreau, John Greenleaf Whittier, William Cullen Bryant, and Walt Whitman.

O'Sullivan wrote a number of pamphlets promoting the Confederate cause, arguing that the presidency had become too powerful and that states' rights needed to be protected against encroachment by the central government.

Towards the end of the Civil War, O'Sullivan appealed to his southern "comrades in arms" to burn Richmond, stating "let every man set fire to his own house".