William Sebastian Cohen (born August 28, 1940) is an author and American politician from the U.S. state of Maine. A Republican, Cohen served as Secretary of Defense (1997–2001) under Democratic President Bill Clinton.
Cohen was born in Bangor, Maine. His mother, Clara (née Hartley), was of Protestant Irish ancestry, while his father, Reuben Cohen, was a Russian Jewish immigrant; the two owned the Bangor Rye Bread Co. Cohen attended Hebrew school as a child. When he was told that he would have to undergo a conversion ceremony, however, he decided not to follow through with the Bar Mitzvah. Instead, he followed his mother's example in refusing to convert to Judaism and became a Christian, specifically within the Unitarian Universalist tradition.
After graduating from Bangor High School in 1958, Cohen attended Bowdoin College, graduating cum laude with a Bachelor of Arts degree in Latin in 1962.