Cohen, William S. (William Sebastian), 1940-

William Sebastian Cohen (born August 28, 1940) is an American politician, lawyer and author. A member of the Republican Party, he represented Maine's 2nd congressional district in the U.S. House of Representatives from 1973 to 1979, as U.S. Senator from Maine from 1979 to 1997, and as Secretary of Defense under President Bill Clinton from 1997 to 2001.

Born in Bangor, Maine, he attended public schools there, graduating from Bangor High School before earning a B.A. from Bowdoin College and an LL.B. from Boston University School of Law. After being admitted to the Maine bar, he commenced practice in Bangor. Cohen served as an assistant county attorney for Penobscot County between 1968 and 1970 and was an instructor at both Husson College and the University of Maine. He served on the Bangor City Council from 1969 to 1972, serving as Mayor from 1971 to 1972.

In the 1972 election, Cohen won a seat in the U.S. House of Representatives, representing Maine's 2nd congressional district. During his first term in Congress, Cohen became deeply involved in the Watergate investigation. As a member of the House Judiciary Committee, he was one of the first Republicans to break with his party and voted for the impeachment of President Richard Nixon. After three terms in the House, Cohen was elected to the U.S. Senate in 1978, defeating incumbent William Hathaway in his first bid for reelection. Cohen was reelected in 1984 and 1990, serving a total of 18 years in the Senate. Cohen developed a reputation as a moderate Republican with liberal views on social issues and has been described as "a career-long maverick with a reputation for fashioning compromise out of discord."

On December 5, 1996, President Bill Clinton announced his selection of Cohen as Secretary of Defense. After confirmation by a unanimous Senate vote, Cohen was sworn in as the 20th Secretary of Defense on January 24, 1997, becoming the first Republican politician to serve a Democratic president in this capacity. In December 1999, Cohen ordered an immediate review of the Clinton administration's controversial "don't ask, don't tell" policy regarding the status and treatment of gays and lesbians in the U.S. military. The order was given shortly after the president said publicly that the policy was not working. During his tenure as Defense Secretary, Cohen also had to address various other social issues, including: the role of women in combat as well as in other military jobs, racism, and sexual harassment.

After leaving the Pentagon in 2001, Cohen founded The Cohen Group, a business consulting and lobbyist firm, with three Pentagon officials, Bob Tyrer, Jim Bodner, and H.K. Park. Cohen has written several books, including mysteries, poetry, and (with George Mitchell) an analysis of the Iran-Contra Affair. He is a Chairman Emeritus of the US-Taiwan Business Council.