Harriet Ruth Harman was born on 30 July 1950 in London, the daughter of John Bishop Harman and Anna Charlotte Harman (née Spicer). She was educated at St Paul's Girls' School, London, and the University of York. She married Jack Dromey in 1982 (died 2022) and they have three children.

She worked at Brent Law Centre, 1974-8, and as legal officer at the National Council for Civil Liberties, 1978-82. In 1982, she was elected as Labour MP for Peckham (later Camberwell and Peckham) in a by-election and she continued to represent the consitutency until she stood down at the general election in 2024. She was Shadow Minister for Social Services, 1984-7, and a Shadow Health Minister, 1987-92. In 1992, she joined the Shadow Cabinet as Shadow Chief Secretary to the Treasury, 1992-4; and Shadow Secretary for Employment, 1994-5; Health, 1995-6; and Social Security, 1996-7.

After the Labour Party won the general election in 1997, she joined the Cabinet as Secretary of State for Social Security and the first Minister for Women, 1997-8. She was later Solicitor General, 2001-5, and Minister of State in the Department of Constitutional Affairs (subsequently the Ministry of Justice), 2005-7. In 2007, she was elected Deputy Leader of the Labour Party and served as Deputy Leader and Chair, 2007-15. She was appointed Lord Privy Seal, Leader of the House of Commons, and Minister for Women and for Equality, 2007-10.

When the Labour Party returned to opposition, she twice served as temporary Leader in 2010 and 2015. During this period she was Shadow Secretary of State for International Development, 2010-11; and Culture Media and Sport, 2011-15; and Shadow Deputy Prime Minister, 2011-15. During the 2015 general election, she led the Woman to Woman campaign. She was recognised as the longest continuously serving woman MP with the title 'Mother of the House' in 2017. She chaired the House of Commons Privileges Committee, 2019-24.

She stood down from the House of Commons and was created a life peer and member of the House of Lords in 2024. She is UK special envoy for women and girls, 2025-, and Chair of the Fawcett Society, 2023-.

Her publications include her memoir, 'A Woman's Work' (2017).