Barbara Castle, Baroness Castle of Blackburn (October 6, 1910 – May 3, 2002), British left-wing politician, was born Barbara Anne Betts in Bradford, Yorkshire, and adopted her family's politics, joining the Labour Party.

After an education at St. Hugh's College, Oxford, she was elected to St. Pancras Borough Council in 1937, and in 1943 she spoke at the annual Labour Party Conference for the first time. She was a senior administrative officer at the Ministry of Food and an ARP warden during the Blitz.

Following her marriage to Ted Castle in 1944, Barbara became a journalist on the Daily Mirror, which by this time had become strongly pro-Labour. In the 1945 general election, which Labour won in a landslide, she became MP for Blackburn, Lancashire. The fiery redhead soon achieved a reputation as a left-winger and a rousing speaker. During the 1950s she was a high-profile Bevanite and made a name for herself as a vocal advocate of decolonisation. In the Wilson government of 1964-1970, she held a succession of ministerial posts. As Minister of Transport, she introduced the breathalyser to combat drink-driving, and as Secretary of State for Employment, she was never far from controversy which reached a fever pitch when the trade unions rebelled against her proposals to reduce their powers in her 1969 white paper, 'In Place of Strife'.

In 1974, after Harold Wilson's defeat of Edward Heath, Castle became Secretary of State for Social Services, but lost her place as a minister after clashing with the new prime minister, James Callaghan, who took over from Wilson in 1976. Despite having taken an anti-European stance in the 1975 referendum debate, she later became a Member of the European Parliament (1979-1989). In 1990, she was created a baroness in her own right (having previously enjoyed the courtesy title of "Lady" as a result of her husband's life peerage, but having refused to use it). She remained active in politics right up until her death, attacking Chancellor Gordon Brown's refusal to link pensions to earnings at the Labour party conference in 2001.

Barbara Castle's autobiography, Fighting All The Way (ISBN 0330328867), was published in 1993.