Frank Alexander Wetmore (June 18, 1886 – December 7, 1978) was an American ornithologist and avian paleontologist.
Wetmore was born at North Freedom, Wisconsin and studied at the University of Kansas. He later studied at George Washington University, receiving his masters degree and doctorate.
Wetmore began federal service in 1910, working for the Biological Survey of the Department of Agriculture.
In 1915, he researched the use of lead shot in causing death in waterfowl. His paleontological research led to his work on the fossil birds Palaeochenoides miocaenus and Nesotrochis debooyi.
In 1925 Wetmore was appointed assistant secretary of the Smithsonian Institution, becoming secretary between 1945 and 1952. In 1939 he was elected a Corresponding Member of the Royal Australasian Ornithologists Union
He wrote A Systematic Classification for the Birds of the World (1930, revised in 1951 and 1960). This Wetmore Order received widespread acceptance, remaining popular until the end of the twentieth century.
He died in Glen Echo, Maryland.
Several taxa of birds have been named in his honor, including the Cretaceous genus Alexornis and the tanagers Wetmorethraupis sterrhopteron and Buthraupis wetmorei.