Walt Whitman (; May 31, 1819 – March 26, 1892) was an American poet, essayist, and journalist. A humanist, he was a part of the transition between transcendentalism and realism, incorporating both views in his works. Whitman is among the most influential poets in the American canon, often called the father of free verse. His work was controversial in its time, particularly his poetry collection Leaves of Grass, which was described as obscene for its overt sensuality. Whitman's own life came under scrutiny for his presumed homosexuality.

Born in Huntington on Long Island, Whitman worked as a journalist, a teacher, and a government clerk. At age 11, he left formal schooling to go to work. As a child and through much of his career he resided in Brooklyn. Whitman's major work, Leaves of Grass, was first published in 1855 with his own money. The work was an attempt at reaching out to the common person with an American epic. He continued expanding and revising it until his death in 1892. During the American Civil War, he went to Washington, D.C. and worked in hospitals caring for the wounded. His poetry often focused on both loss and healing. Two of his well known poems, "O Captain! My Captain!" and "When Lilacs Last in the Dooryard Bloom'd", were written on the death of Abraham Lincoln. After a stroke towards the end of his life, Whitman moved to Camden, New Jersey, where his health further declined. When he died at age 72, his funeral was a public event.

Whitman's influence on poetry remains strong. Mary Smith Whitall Costelloe argued: "You cannot really understand America without Walt Whitman, without Leaves of Grass ... He has expressed that civilization, 'up to date,' as he would say, and no student of the philosophy of history can do without him." Modernist poet Ezra Pound called Whitman "America's poet ... He is America."