The Gulag Archipelago: An Experiment in Literary Investigation (Russian: Архипелаг ГУЛАГ, romanized: Arkhipelag GULAG) is a three-volume nonfiction series written between 1958 and 1968 by Russian writer Aleksandr Solzhenitsyn, a Soviet dissident. It was first published in 1973 by the Parisian publisher YMCA-Press, and it was translated into English and French the following year. It explores a vision of life in what is often known as the Gulag, the Soviet labour camp system. Solzhenitsyn constructed his highly detailed narrative from various sources including reports, interviews, statements, diaries, legal documents, and his own experience as a Gulag prisoner.

Following its publication, the book was initially circulated in the Soviet Union by samizdat underground publication. It was not widely published there until 1989. It appeared that year in the literary journal Novy Mir; a third of the work was published in three issues. Since the dissolution of the Soviet Union, The Gulag Archipelago has been officially published in Russia.

As structured in most printed editions, the text comprises seven sections divided into three volumes: parts 1 and 2, parts 3 and 4, and parts 5 to 7. At one level, the Gulag Archipelago traces the history of the system of forced labor camps that operated in the Soviet Union from 1918 to 1956. Solzhenitsyn begins with Vladimir Lenin's original decrees that were made shortly after the October Revolution; they established the legal and practical framework for a series of camps where political prisoners and ordinary criminals would be sentenced to forced labor.^{Note 2}

The book describes and discusses the waves of purges and the assembling of show trials by Stalin through the 1930s in the context of the development of the greater Gulag system; Solzhenitsyn closely examines its purposive legal and bureaucratic development. The narrative ends in 1956 at the time of Nikita Khrushchev's Secret Speech ("On the Personality Cult and its Consequences"). Khrushchev gave the speech at the 20th Congress of the Communist Party of the Soviet Union, denouncing Joseph Stalin's personality cult, his autocratic power, and the widespread surveillance of all classes of people that pervaded the Stalin era.

Parallel to this historical and legal narrative, Solzhenitsyn follows the typical course of a zek through the Gulag. This was a slang term for an inmate, derived from the widely used abbreviation z/k for zakliuchenny ("prisoner"). He started with arrest, show trial, and initial internment, continuing with the transport to the Gulag. In that setting, he explored the treatment of prisoners and their general living conditions, slave labor gangs and the technical prison camp system, camp rebellions and strikes, such as the Kengir uprising; the practice of continued internal exile following the completion of the original prison sentence, and the ultimate but not guaranteed release of the prisoner, if one survived. Solzhenitsyn's examination details the trivial and commonplace events of an average prisoner's life, as well as specific and noteworthy events during the history of the Gulag system, including revolts and uprisings.

At Chapter 4, Solzhenitsyn writes: "Macbeth’s self-justifications were feeble – and his conscience devoured him. Yes, even Iago was a little lamb, too. The imagination and spiritual strength of Shakespeare's evildoers stopped short at a dozen corpses. Because they had no ideology. Ideology – that is what gives evildoing its long-sought justification and gives the evildoer the necessary steadfastness and determination. That is the social theory which helps to make his acts seem good instead of bad in his own and others' eyes.... That was how the agents of the Inquisition fortified their wills: by invoking Christianity; the conquerors of foreign lands, by extolling the grandeur of their Motherland; the colonizers, by civilization; the Nazis, by race; and the Jacobins (early and late), by equality, brotherhood, and the happiness of future generations... Without evildoers there would have been no Archipelago."

Solzhenitsyn painstakingly laid the theoretical, legal, and practical origins of the Gulag system at Lenin's feet, not Stalin's. According to Solzhenitsyn's testimony, Stalin amplified a concentration camp system that was already in place and this was significant because he said many Western intellectuals considered the Soviet prison camp system to be a Stalinist aberration.

Solzhenitsyn claims that although many practices had been stopped, the basic structure of the system had survived and it could be revived and expanded by future leaders. While Khrushchev, the Communist Party, and the Soviet Union's supporters in the West viewed the Gulag as a deviation of Stalin, Solzhenitsyn and others among the opposition tended to view it as a systemic fault of Soviet political culture, and an inevitable outcome of the Bolshevik political project.