Breslov (also Bratslav, also spelled Breslev) is a branch of Hasidic Judaism founded by Rebbe Nachman of Breslov (1772–1810), a great-grandson of the Baal Shem Tov, founder of Hasidism. Its adherents strive to develop an intense, joyous relationship with God, and receive guidance toward this goal from the teachings of Rebbe Nachman.

The movement has had no central, living leader for the past 200 years, as Rebbe Nachman did not designate a successor. As such, they are sometimes referred to as the טויטע חסידים (the "Dead Hasidim"), since they have never had another formal Rebbe since Nachman's death. However, certain groups and communities under the Breslov banner refer to their leaders as "Rebbe".

The movement weathered strong opposition from virtually all other Hasidic movements in Ukraine throughout the 19th century, yet, at the same time, experienced growth in numbers of followers from Ukraine, Belarus, Lithuania, and Poland. By World War I, thousands of Breslov Hasidim were located in those places. After the Bolshevik Revolution, Communist crackdowns forced the movement underground in Russia. Thousands of Hasidim were imprisoned or executed during Stalin's Great Purge of the 1930s, and killed by the Nazis, who invaded the Soviet Union in 1941. The movement was regenerated in the United Kingdom, the United States, and Israel, by those who escaped, with large numbers of Yemenite Jews and other Mizrahim joining the sect.