O Pioneers! is a 1913 novel by American author Willa Cather, written while she was living in New York. It was her second published novel. The title is a reference to a poem by Walt Whitman entitled "Pioneers! O Pioneers!" from Leaves of Grass (1855).

Willa Sibert Cather was an American writer known for her novels of life on the Great Plains, including O Pioneers!, The Song of the Lark, and My Ántonia. In 1923, she was awarded the Pulitzer Prize for One of Ours, a novel set during World War I.