William Thornton Innes III, L.H.D. (February 2, 1874 – February 27, 1969) was an American aquarist, author, photographer, printer and publisher. Innes was the author of numerous influential books and hundreds of articles about aquarium fish, aquatic plants and aquarium maintenance during the formative years of the aquarium hobby in America. Born in Philadelphia, he was the founder, publisher and editor of The Aquarium, the first successful national magazine on the subject of keeping freshwater tropical fishes. The magazine ran monthly for thirty-five years from May 1932 through January 1967.
Graduating from Friends’ Central School, Philadelphia, he entered the printing concern of his father, in 1895. In 1899 he married Mary Weber Weaver. From the 1920s he organized aquarium shows in Philadelphia’s Horticultural Hall.