Alan James Carter Duncan (born March 31, 1957) is an English politician, and member of Parliament for Rutland and Melton. He is a member of the Conservative Party, and sits on the front bench as Shadow Secretary of State for Constitutional Affairs.

He is a libertarian, wishing to minimize the state, whilst also seeking to abolish laws against drugs. He is on the council of the Conservative Way Forward group. He was the first Conservative MP to openly acknowledge being gay.