Sidney Irving Smith (February 18, 1843, in Norway, Maine – May 6, 1926, in New Haven, Connecticut)[1] was an American zoologist.

[1] Smith suffered from hereditary glaucoma, rendering him partially sighted from 1906, and completely blind some years before his death.

He stayed on at Yale, initially as an assistant, but from 1875 as the first professor of comparative anatomy, a post he retained until his retirement in 1906.

Smith was the chief zoologist during the dredging of Lake Superior carried out by the United States Lake Survey in 1871, and the dredging in the region of St. George's Banks in 1872 carried out by the United States Coast Survey.

[3] Sidney Irving Smith was honoured in the specific epithets of a number of species.