Bevanism was the ideological argument for the Bevanites, a movement on the left wing of the Labour Party in the late 1950s and typified by Aneurin Bevan. Also called 'the Old Left', it was named after its dominant personality; however its intellectual direction was given by Richard Crossman and his followers including Michael Foot and Barbara Castle. Bevanism was opposed by the Gaitskellites, who are variously described as centre-left, social democrats, or "moderates" within the party.  The Gaitskellites typically won most of the battles inside Parliament, but Bevanism was stronger among local Labour activists. Bevanites split over the issue of nuclear weapons, and the movement faded away after Bevan died in 1960.
Bevanism was influenced by Marxism, with biographer and later Leader of the Labour Party Michael Foot saying that Bevan's "belief in the class struggle stayed unshaken", while acknowledging that Bevan was not a traditional Marxist. Despite declaring inspiration from Marx, Bevan did not visibly support insurrectionist concepts of proletarian revolution, arguing that revolution depended on the circumstances, or the Leninist organisational model of democratic centralism typical of many Communist parties. According to Ed Balls, Bevan and his supporters instead preferred a strident but pluralist conception of democratic socialism, tempered by pragmatic sensibilities and practical application.
The Bevanite Group of MPs, of which there were about 3 dozen, coalesced following Bevan's resignation from the Cabinet in 1951 when the health service started charging for previously free services such as spectacles in order to help pay for Britain's involvement in the Korean War. Bevanites Harold Wilson and John Freeman resigned with Bevan himself. The group in Parliament drew heavily from the previous "Keep Left" group, which had previously dissented from the pro-American foreign policy of the 1945–1951 Labour government favoured by Clement Attlee, his Foreign Secretary Ernest Bevin and Hugh Gaitskell. According to Crossman in December 1951 the group was not organised, and Bevan could not be persuaded to have any consistent or coherent strategy, but they did have a group who met regularly and liked each other and came to represent "real Socialism" to a large number of Party members. Picture Post called them the "Bevanly Host" in April 1952.
Bevanites organised in Constituency Labour Parties across Britain, and set up local discussion groups known as "Brains Trusts", also a legacy of the "Keep Left" group.
Brains Trusts organised in support of the newspaper favoured by Bevanites, Tribune magazine, allocating left-wing MPs and campaigners to form speaking panels around the country. Tribune itself provided an important print voice for Bevanite politicians and was in wide circulation.
The main Bevanite objectives were:
In the early 1950s Bevanites advocated:
Historian Kenneth O. Morgan says. "Bevan alone kept the flag of left-wing socialism aloft throughout — which gave him a matchless authority amongst the constituency parties and in party conference." At the 1952 Labour Party Conference Bevanites were elected to six of the seven places on the National Executive Committee by constituency representatives.
Later in his political career, Bevan began advocating the maintenance of Britain's nuclear deterrent, against those who became associated with the Campaign for Nuclear Disarmament (CND), saying that without them a future British foreign secretary would be going "naked into the conference chamber". This split the Bevanites with many, such as leading Bevanite Michael Foot, continuing to oppose Britain's nuclear weapons, with Labour's 1983 manifesto under Foot's leadership of the party calling for unilateral nuclear disarmament.