Nesta Helen Webster (née Bevan, 24 August 1876 – 16 May 1960) was an English author who revived theories about the Illuminati. She claimed that the secret society's members were occultists, plotting communist world domination, through a Jewish cabal, the Masons and Jesuits. She blamed the group for events including the French Revolution, 1848 Revolution, the First World War, and the Bolshevik Revolution. Her writing influenced later conspiracy theories and ideologies, including American anti-communism (particularly the John Birch Society) and the militia movement.

In 1920, Webster became a contributor to The Jewish Peril, a series of articles in the London Morning Post centered on the forged document The Protocols of the Elders of Zion. These articles were compiled and published in the same year in book form under the title of The Cause of World Unrest. Webster claimed that the authenticity of the Protocols of the Elders of Zion was an "open question". Prior to World War II, Webster was involved in Fascist political groups in the United Kingdom.