Marcia Matilda Falkender, Baroness Falkender (born March 10, 1932) is a British Labour politician, being first the private secretary for, and then the political secretary and head of political office to, Harold Wilson. She is thought to have been one of the principal sources of true stories behind the Yes, Minister series.

Educated at Northampton High School for Girls and reading a BA in History at Queen Mary College of the University of London, she became secretary to the General Secretary of the Labour Party in 1955; a year later, in 1956, she became Harold Wilson's private secretary, a position she remained in until 1964, when she rose to be his political secretary and head of political office in his position as Leader of the Labour Party and as Prime Minister from 1964 until 1970 and again from 1974 till 1976.

She was elevated to the Peerage as Baroness Falkender on July 11, 1974.

She married George Edmund Charles Williams in 1955, and divorced him in 1961, but continued to be known as Marcia Williams in her professional life.

After retiring, she worked as a columnist for the Mail on Sunday from 1983–1988

Private Eye often referred to her as "Forkbender". She is thought to have played a significant rôle in the development of the Yes, Minister series, providing a number of true stories that formed the bases of the programmes.