Avrohom Bornsztain, also spelled Avraham Borenstein or Bernstein, was a leading posek in late-nineteenth-century Europe and founder and first Rebbe of the Sochatchover Hasidic dynasty. He is known as the Avnei Nezer after the title of his posthumously-published set of Torah responsa, which is widely acknowledged as a halakhic classic. His only son, Shmuel, author of Shem Mishmuel, succeeded him as Rebbe.