William David Thomas (March 22, 1880 – May 17, 1936) was an American pharmacist and politician from Hoosick Falls, New York. A Republican, he was most notable for his service as a member of the United States House of Representatives from New York, a position he held from 1934 until his death. A native of Middle Granville, New York, Thomas graduated from Albany College of Pharmacy in 1904 and settled in Hoosick Falls, where he operated a pharmacy. Thomas also became involved in banking and other business ventures.