Bruno Bauer (; German: [baʊɐ]; 6 September 1809 – 13 April 1882) was a German philosopher, theologian, historian, and biblical critic. A prominent member of the Young Hegelians, he was a radical rationalist critic of the Bible and Christianity. Initially a student of Georg Wilhelm Friedrich Hegel, Bauer became a central figure in the intellectual circles of the Vormärz, the period preceding the Revolutions of 1848. His philosophical work was a major influence on, and target of critique for, Karl Marx and Friedrich Engels, with whom he had a close but tumultuous relationship.
Starting as a right-wing Hegelian, Bauer shifted to the left in 1839, developing a radical critique of religion and the state. He argued that the Christian gospels were not historical records but literary works of the human self-consciousness. His most significant work of this period, The Trumpet of the Last Judgement over Hegel the Atheist and Antichrist (1841), presented Hegel's philosophy as a revolutionary atheism that called for the overthrow of all existing religious and political institutions. Bauer's political thought was a form of republicanism based on the concept of "infinite self-consciousness," an ethical idealism that advocated for the constant transformation of society in pursuit of rational freedom.