RADZYN (Pol. Radzyń-Podlaski; Rus. Radin), district capital in the province of Lublin, E. Poland. Founded in 1468, the town was first named Koźirynek. Although no reliable evidence is available, it has been assumed that Jews lived in Radzyn from its foundation. In 1765 there were 537 Jews living there. The town developed during the 19th century. There were 1,301 Jews (about 53% of the total population) by 1856 and 2,853 (53.5% of the total population) in 1897. During World War I the general population decreased, but in 1921 there were still 2,895 Jews (59.7%) in Radzyn, and an estimated 3,000 on the eve of World War II.
The synagogue, a single-story stone building, was erected at the beginning of the 19th century. Among the outstanding personalities of the community was Gershon Ḥanokh Leiner, founder of the Radzyn dynasty of Ḥasidim, who reintroduced the interweaving of the blue thread among the ẓizit and established a laboratory for producing the proper color. His grandson, Samuel Solomon Leiner, also a leader of the Radzyn Ḥasidim, perished in the Holocaust. Prominent rabbis of Radzyn were Simeon Deutsch, who held office during the first half of the 19th century, and Ḥayyim Fein (d. during World War II). Jewish economic life was affected by a fire which destroyed many homes in 1929, and many Jewish families became dependent on support from their coreligionists in other communities. During the 1930s an economic crisis and the anti-Jewish economic *boycott proclaimed by Polish antisemites also undermined Jewish economic life. In the democratic elections to the community's council (1931) two Zionists, two Ḥasidim, two representatives of the craftsmen, one of the socialist craftsmen, and two representatives of the battei midrash were elected.
Sefer Radzyn (Heb. and Yid., 1957).