Pitirim Alexandrovich Sorokin (/səˈroʊkɪn, sɔː-/; Russian: Питирим Александрович Сорокин; 4 February [O.S. 23 January] 1889 – 10 February 1968) was a Russian American sociologist and political activist, who contributed to the social cycle theory.

Sorokin was a professor at Saint Petersburg Imperial University, three times imprisoned by the Czarist regime for "revolutionary activity." His active opposition to the Bolsheviks led, after they were in power, to his arrest and sentence to death. Only with the help and intervention of friends, including Thomas Masaryk and Edouard Benes, was his sentence commuted to permanent exile, which led Sorokin to flee to Czechoslovakia.

Moving to the United States, he became a professor of sociology at the University of Minnesota in 1924, and, in 1930, he was hired as head of the newly formed department of sociology at Harvard University.

Pitirim Alexandrovich Sorokin was born on 4 February [O.S. 23 January] 1889, in Turya, a small village in Yarensky Uyezd, Vologda Governorate, Russian Empire (now Knyazhpogostsky District, Komi Republic, Russia), the second son to a Russian father and Komi mother. Sorokin's father, Alexander Prokopievich Sorokin, was from Veliky Ustyug and a traveling craftsman specializing in gold and silver. At the same time, while his mother, Pelageya Vasilievna, was a native of Zheshart and belonged to a peasant family. Vasily, his elder brother, was born in 1885, and his younger brother, Prokopy, was born in 1893. Sorokin's mother died on March 7, 1894, in the village of Kokvitsa. After her death Sorokin and his elder brother Vasily stayed with their father, traveling with him through the towns searching for work. At the same time, Prokopy was taken in by his aunt, Anisya Vasilievna Rimsky. The latter lived with her husband, Vasily Ivanovich, in the village of Rimia. Sorokin's childhood, spent among the Komi, was complicated, but enriched by a religious and moral education. The moral qualities (such as piety, a firm belief in good and love) cultivated in him at that time would yield their fruits in his subsequent work (his amitology and call to overcome the crisis of modernity).

Pitirim's and his older brother's father developed alcoholism. Because of this, their father had severe anxiety and panic attacks to the point where he was physically abusive to his sons. After a brutal beating that left a scar on Pitirim's upper lip, Pitirim, at the age of eleven, along with his older brother, decided that he wanted to be independent and no longer under their father's care.

Sorokin was anti-Czarist. He was arrested at the age of 17. He was arrested twice more for his anti-Czarist activities.

In the early 1900s, supporting himself as an artisan and clerk, Sorokin attended the Saint Petersburg Imperial University in Saint Petersburg, where he earned his graduate degree in criminology and became a professor.

Sorokin was an anti-communist. During the Russian Revolution he was a member of the Socialist Revolutionary Party, a deputy of the Russian Constituent Assembly, a supporter of the White movement, and a secretary to Prime Minister Alexander Kerensky. After the October Revolution, Sorokin continued to fight communist leaders and was arrested by the new regime several times before he was eventually condemned to death. After six weeks in prison, Sorokin was released and went back to teaching at the University of Saint Petersburg, becoming the founder of the sociology department at the university. As he had been a leader among the Democrats leading up to the Russian Revolution, he was sought by Vladimir Lenin's forces after Lenin consolidated his power.