This article is about the socialist politician. For the children's author, see Beatrix Potter.

Martha Beatrice Potter Webb (January 22, 1858 - April 30, 1943) was a British socialist, economist and reformer, usually referred to in the same breath as her husband, Sidney Webb. Although her husband became Baron Passfield in 1929, she refused to be known as Lady Passfield.

Beatrice Webb was born in Gloucester, Gloucestershire, the granddaughter of a Radical MP, Richard Potter. In 1882, she had a relationship with Radical politician Joseph Chamberlain, by then a Cabinet minister. This was a failure, and in 1890 she was introduced to Sidney Webb, whose help she sought in research she was carrying out. They married in 1892, and remained together for the rest of her life. She was an active partner in all his political and professional activities, including the organisation of the Fabian Society and the establishment of the London School of Economics. She co-authored books such as the History of Trade Unionism (1894), and was co-founder of the New Statesman magazine (1913).

In H.G. Wells's The New Machiavelli (1911), the Webbs, as 'the Baileys', are unmercifully lampooned as short-sighted, bourgeois manipulators. The Fabian Society, of which Wells was briefly a member (1903-08), fares no better in his estimation.

Webb's nephew, Sir Stafford Cripps, became a well-known British Labour politician in the 1930s and 1940s.