Wesley Duaine Sweetser (1919–2006) was an American literary scholar.
Born in National City, California, United States, he attended the University of Colorado, where he gained a Ph.D. for a thesis on Welsh writer Arthur Machen.
His enthusiasm for Machen led him to publish a valuable biography of the author based on his earlier thesis and, with Adrian Goldstone, a Machen bibliography. He played an important part in supporting the 1960s revival in Machen's works.
Sweetser also served for a long period in the United States Air Force, reaching the rank of major.