Nineteen Eighty-Four, often referred to as 1984, is a dystopian social science fiction novel by the English novelist George Orwell (the pen name of Eric Arthur Blair). It was published on 8 June 1949 by Secker and Warburg as Orwell's ninth and final book completed in his lifetime. Thematically, Nineteen Eighty-Four centres on the consequences of totalitarianism, mass surveillance, and repressive regimentation of persons and behaviours within society. Orwell, himself a democratic socialist, modelled the totalitarian government in the novel after Stalinist Russia and Nazi Germany. More broadly, the novel examines the role of truth and facts within politics and the ways in which they are manipulated.

The story takes place in an imagined future, the year 1984, when much of the world has fallen victim to perpetual war, omnipresent government surveillance, historical negationism, and propaganda. Great Britain, known as Airstrip One, has become a province of a totalitarian superstate named Oceania that is ruled by the Party who employ the Thought Police to persecute individuality and independent thinking. Big Brother, the leader of the Party, enjoys an intense cult of personality despite the fact that he may not even exist. The protagonist, Winston Smith, is a diligent and skillful rank-and-file worker and Outer Party member who secretly hates the Party and dreams of rebellion. He enters into a forbidden relationship with a colleague, Julia, and starts to remember what life was like before the Party came to power.

Nineteen Eighty-Four has become a classic literary example of political and dystopian fiction. It also popularised the term "Orwellian" as an adjective, with many terms used in the novel entering common usage, including "Big Brother", "doublethink", "Thought Police", "thoughtcrime", "Newspeak", "memory hole", "2 + 2 = 5", and "proles". Time included it on its 100 best English-language novels from 1923 to 2005. It was placed on the Modern Library's 100 Best Novels, reaching No. 13 on the editors' list and No. 6 on the readers' list. In 2003, the novel was listed at No. 8 on The Big Read survey by the BBC. Parallels have been drawn between the novel's subject matter and real life instances of totalitarianism, mass surveillance, and violations of freedom of expression among other themes.