My Mortal Enemy is the eighth novel by American author Willa Cather. It was first published in 1926.

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.