Jennifer Formby (née Sandle; born 12 April 1960) is a British trade unionist and political figure who served as General Secretary of the Labour Party from 2018 to 2020.

Born Jennifer Sandle in London, her father served in the Royal Navy in Korea, Suez and Lebanon.

[1][2] Formby became a trade unionist when she began her working life in Salisbury at the bookmakers William Hill in the late 1970s, and became a branch secretary in Unite's predecessor, the Transport and General Workers' Union.

[9] In February 2018, Formby announced she was a candidate to become General Secretary of the Labour Party, shortly after the incumbent, Iain McNicol, resigned.

[10] Her main rival, Jon Lansman, the chair of Momentum, dropped out of contention on 11 March, making Formby the frontrunner.