Fiona Margaret Mactaggart (born 12 September 1953) is a politician in the United Kingdom. She is Labour member of Parliament for Slough and at the Home Office serves as Parliamentary Under-Secretary of State with responsibility for Race Equality, Community Policy and Civil Renewal.

She was first elected to Parliament in 1997. She was a councillor and Leader of the Labour Group on Wandsworth Council from 1988 to 1990. She has been a primary school teacher and Chair of Liberty.

Her father, the late Sir Ian Mactaggart Bt, was a multimillionaire Glasgow property developer, Tory candidate and Europhobe. Her mother's father, Sir Herbert Williams Bt, was a Conservative Member of Parliament for 27 years. Her great-grandfather however was Sir John Mactaggart, the first treasurer of the first ever branch of Keir Hardie's Labour party.