Mordechai Dovid Unger (Hebrew: הרב מרדכי דוד אונגער, born 1954) is the first Rebbe of Bobov-45.

[1] Following the death of his father-in-law right before the Purim holiday in 2005,[3] a dispute arose as to who should be the Grand Rebbe of the then 120,000 Bobov Hasidim worldwide.

[1] Unger could not challenge his own father for leadership of Dombrov, which anyway was not as substantial a dynasty as Bobov.

[4] The matter of succession was brought before a beth din (religious court) in 2007, which ruled that Halberstam would be declared Rebbe of Bobov (אדמו"ר מבאבוב) with its headquarters on 48th Street in Borough Park, Brooklyn,[5] while Unger would be Rebbe of Bobov-45 (אדמו"ר מבאבוב-45), located on 45th Street.

[5][6] Brooklyn Borough President Eric Adams visited Bobov–45 as part of his 2017 re-election campaign.