Ambrose Gwinnett Bierce (June 24, 1842 – circa 1914) was an American short story writer, journalist, poet, and Civil War veteran.

Bierce's book The Devil's Dictionary was named as one of "The 100 Greatest Masterpieces of American Literature" by the American Revolution Bicentennial Administration. His story "An Occurrence at Owl Creek Bridge" has been described as "one of the most famous and frequently anthologized stories in American literature"; and his book Tales of Soldiers and Civilians (also published as In the Midst of Life) was named by the Grolier Club as one of the 100 most influential American books printed before 1900.

A prolific and versatile writer, Bierce was regarded as one of the most influential journalists in the United States, and as a pioneering writer of realist fiction. For his horror writing, Michael Dirda ranked him alongside Edgar Allan Poe and H. P. Lovecraft. His war stories influenced Stephen Crane, Ernest Hemingway, and others, and he was considered an influential and feared literary critic. In recent decades Bierce has gained wider respect as a fabulist and for his poetry.

In December 1913, Bierce traveled to Chihuahua, Mexico, to gain first-hand experience of the Mexican Revolution. He disappeared, and was rumored to be traveling with rebel troops. He was never seen again.