William Townsend Pheiffer (July 15, 1898 – August 16, 1986) was an American lawyer, Republican politician and diplomat. He was a Representative from New York in the 77th Congress and ambassador to the Dominican Republic.
He was born in Purcell, Indian Territory (now Oklahoma), the son of William Pfeiffer (1869-?) and Susan Garfinkel (1869-?). His brother was Harry R. Pfeiffer (1896-?). His father was a lawyer. His maternal uncle was Julius Garfinckel, wealthy merchant. He attended the public schools of Purcell, Ardmore and Oklahoma City, and the University of Southern California, where he was a member of the Chi Phi Fraternity.
During World War I, Pheiffer served as a private in the cavalry of the U.S. Army, in 1918. He earned a law degree at the law school of the University of Oklahoma, in 1919. That same year, he was admitted to the bar and began working in general practice like his father. He practiced in Sayre, Oklahoma, from 1923 to 1926. In 1924, he was a candidate for the 2nd District in the Oklahoma Senate.