William Trelease (February 22, 1857, Mount Vernon, New York – January 1, 1945) was an American botanist, entomologist, explorer, writer and educator. This botanist is denoted by the author abbreviation Trel. when citing a botanical name.Trelease graduated B.S. from Cornell University in 1880. He was instructor in botany at Harvard University 1880-81, instructor in botany at the University of Wisconsin 1881-83, and professor of botany there from 1883 to 1885.