Decline and Fall is a novel by the English author Evelyn Waugh, first published in 1928. It was Waugh's first published novel; an earlier attempt, entitled The Temple at Thatch, was destroyed by Waugh while still in manuscript form. Decline and Fall is based in part on Waugh's undergraduate years at Hertford College, Oxford, and his experience as a teacher in Wales. It is a social satire that employs the author's characteristic black humour in lampooning various features of British society in the 1920s.

The novel's title is a contraction of Edward Gibbon's The History of the Decline and Fall of the Roman Empire. The title alludes also to the German philosopher Oswald Spengler's The Decline of the West (1918–1922), which first appeared in an English translation in 1926 and which argued, among other things, that the rise of nations and cultures is inevitably followed by their eclipse. Waugh read both Gibbon and Spengler while writing his first novel. Waugh's satire is unambiguously hostile to much that was in vogue in the late 1920s, and "themes of cultural confusion, moral disorientation and social bedlam...both drive the novel forward and fuel its humour." This "undertow of moral seriousness provides a crucial tension within [Waugh's novels], but it does not dominate them." Waugh himself stated boldly in his 'Authors Note' to the first edition: 'Please bear in mind throughout that IT IS MEANT TO BE FUNNY.'