William Louis Pfeiffer (May 29, 1907 – July 22, 1985) was a Republican politician who served one term as a member of the United States House of Representatives from New York.

In 1938 he was appointed chief staff aide for the New York State Republican Congressional Committee.

After leaving Congress Pfeiffer relocated to Kattskill Bay and pursued a banking career.

He was a board of directors member and executive committee chairman for the Bank of North America in New York City from 1952 to 1966.

Pfeiffer maintained an interest in Republican politics, and successfully managed the campaigns of Nelson Rockefeller for Governor of New York in 1962 and 1966.