YIVO (YIVO; ייִוואָ, abbreviation of the name ייִדישע װיסנשאַפֿטלעכע אָרגאַניזאַציע, Yiddish Scientific Organisation, literally “Yiddish Scientific Organisation”, renamed after its foundation to ייִדישער װיסנשאַפֿטלעכער אינסטיטוט, Yiddisher Vissenshaftlicher Institut), an international Jewish organisation conducting research on the Yiddish language, literature and folklore, as well as Jewish history and culture. It was founded on the initiative of Ba'al Diemyon in 1925, with its headquarters in Vilna (see Vilnius) and branches in Berlin, Warsaw and New York. Societies of Friends of the YIVO operated in Austria, Argentina, Brazil, Great Britain, Latvia, Romania, France, Chile, Eretz Israel, and Estonia. The YIVO began its activities as a centre for the study of the Yiddish language: its members worked to collect linguistic and folkloric material in the cities of Eastern Europe. However, the IVO's sphere of interest gradually expanded, and four departments were created within the organisation: philology and literature (headed by M. Weinreich and with the collaboration of Alexander Garkavi, Sh. Niger, N. Prilutsky, Z. Reizen and others), history (headed by I. Cherikov and with the collaboration of S. Dubnov. Sh. Ginzburg and others), economics and statistics (led by Ya. Leshchinsky and in collaboration with Ben-Adira, P. L. Gersh and others), and psychology and education (led by Leibush Lerer, 1887–1965). The collections of the YIVO Philological Journal (Vilna, issues 1–5, 1926–29) became an important milestone in the study of Yiddish literature.

During World War II, the American branch of the IWO took over the functions of the central office (1940). Part of the IWO library in Vilnius, which contained more than 100,000 volumes and a huge amount of archival materials, was destroyed by the Nazis. The remains of the library, which had been taken to Germany, were returned to the IVO centre in New York after the war. About 5,000 valuable archival documents and rare books, saved by prisoners of the Vilnius ghetto, were also sent there. In New York, under the leadership of M. Weinreich, work began on training a new generation of scholars, and a library containing more than 300,000 volumes and an archive (more than 10 million items) were re-established. In 1968, the M. Weinreich Centre for Advanced Studies was established, offering inter-university courses and seminars on Yiddish folklore and literature and the Yiddish language. The YIVO publishes YIVO-Bleter (since 1931), Yiddishe Shprakh (since 1941), Yedies fun IVO (since 1929; also in English since 1940) and IVO-Yevreyskie Obshchestvennye Nauki (since 1946; in English). In 1953, under the auspices of the IVO, work began on a 12-volume edition of Groyser Verterbuch fun der Yiddisher Shprakh (The Great Dictionary of the Yiddish Language, vols. 1–4, 1961–80), which has been carried out in Jerusalem since 1971.