Bobov-45 (Hebrew 45-חסידות באבוב) is a Hasidic sect within Haredi Judaism. An offshoot of the larger Bobov Hasidic dynasty originating in Bobowa, Galicia, Southern Poland, Bobov-45 is headquartered in the neighborhood of Borough Park in Brooklyn, New York. It has branches in the Williamsburg section of Brooklyn, Monsey, New York, and in Manchester and London, England. In Israel, Bobov-45 has branches in Jerusalem, Bnei Brak, Elad, and Betar Illit.
Mordechai Dovid Unger is the first, and current, Grand Rabbi of Bobov-45. He is the younger son-in-law of the Fourth Bobover Rebbe, Grand Rabbi Naftali Zvi Halberstam. Yehoshua Rubin, the older son-in-law of Halberstam, is the current dayan and rabbinical leader of the sect.
In 2005, after the death of the Fourth Bobover Rebbe, Grand Rabbi Naftali Halberstam, a breakaway group of Bobover Hasidim set up a grand hall in Brooklyn on 45th Street under the leadership of Mordechai Dovid Unger, Halberstam's younger son in law. Halberstam himself had no sons. A leadership dispute then arose between Unger and Ben Zion Aryeh Leibish Halberstam, brother of the previous Rebbe and son of the Third Bobover Rebbe, Grand Rabbi Shlomo Halberstam, who both claimed the title of Bobover Rebbe. The dispute was taken to an arbitration panel, known as a Beth Din, which ruled that the faction following Ben Zion Aryeh Leibish Halberstam held the rights to the name "Bobov". Unger was also allowed to use the name Bobov, so long as a distinguishing identifier would be added to it. The qualifying suffix "-45" was henceforth adopted in tribute to the name of the street on which the community center of the sect was located at the time. In addition, the Beth din ordered Bobov to pay $6,200,000 to Bobov-45's Rebbe and Rav in 25 quarterly installments as an allotment of their faction's share of the inheritance of the larger Bobov enterprise's assets, valued at the time at over $100,000,000. The award was based upon the number of members in the two communities.
In addition to those books revered by all Hasidim, the Bobov-45er Hasidim particularly treasure the teachings of the fourth Bobover Rebbe. The versions of the siddur used by Bobov-45 Hasidim is called Tfilas Rav.