Warren Crawford Cowgill (December 19, 1929 – June 20, 1985) was an American linguist. He was a professor of linguistics at Yale University and the Encyclopædia Britannica's authority on Indo-European linguistics. Two separate Indo-European sound laws are named after him, Cowgill's law of Greek and Cowgill's law of Germanic. Cowgill was unusual among Indo-European linguists of his time in believing that Indo-European should be classified as a branch of Indo-Hittite, with Hittite as a sister language of the Indo-European languages, rather than a daughter language. Warren Cowgill and his twin brother, anthropologist George Cowgill, were born near Grangeville, Idaho. Along with his brother, he graduated from Stanford University in 1952 and received a Ph.D. from Yale in 1957. He was a member of the Yale faculty in the Department of Linguistics until his death in 1985.