Mordechai Yosef Leiner of Izbica (Yiddish: איזשביצא, איזביצא Izhbitza, Izbitse, Ishbitza) (1801-1854) was a rabbinic Hasidic thinker and founder of the Izhbitza-Radzyn dynasty of Hasidic Judaism. Rabbi Mordechai Yosef was born in Tomashov (Polish: Tomaszów) in 1801 to his father Reb Yaakov the son of Reb Mordechai of Sekul, a descendant of Rabbi Shoul Wahl. At the age two he became orphaned of his father. He became a disciple of Reb Simcha Bunim of Peshischa where he joined Rabbi Menachem Mendel of Kotzk and Rabbi Yosef of Yartshev; both were also born in Tomashov. When Rabbi Menachem Mendel became Rebbe in Kotzk, Reb Morechai Yosef became his disciple there; then in 1839 became himself a rebbe in Tomaszów, moving subsequently to Izbica.