Rabbi Aryeh Leib ben Asher Gunzberg, known as the Shaagas Aryeh after his principal work, was born in 5455 (1695); according to several sources he was born in Pinsk, where his father, Rabbi Asher, headed the rabbinical court. His grandfather was Rabbi Leib, nicknamed the Baal HaTosafot. Already in his youth he was recognized as a prodigy.

When his father became rabbi of Minsk, he assisted him in communal affairs and founded a renowned yeshiva there. A dispute with the city's rabbi, Rabbi Yechiel Heilprin, author of Seder HaDorot, forced him to leave Minsk. Around the middle of the century he became rabbi of Volozhin and headed a yeshiva there; Rabbi Chaim of Volozhin was among his students. For many years he lived in poverty, wandering from town to town.

In 1765, at nearly seventy, he was appointed rabbi, head of the rabbinical court and rosh yeshiva of Metz, in France, a post he held for about twenty years until his death. Having lost his sight in old age, he continued to study from memory.

He was famed for his sharp mind and the strength of his reasoning. Although he had taught pilpul in his Minsk yeshiva, he opposed that method and sought the plain meaning of the sources, studying the Talmud and the Rishonim without relying on the Acharonim. He did not hesitate to dispute accepted positions, or to rule leniently on his own when he was certain something was permitted, which led to many conflicts with communal leaders. For himself, he was strict about the prohibition of chadash.

Works: Shaagas Aryeh, responsa first published in 1755, mainly on Orach Chaim; Turei Even, novellae on the tractates Rosh Hashanah, Chagigah and Megillah; Gevuras Ari, on Taanit, Yoma and Makkot.

He passed away in Metz on 15 Tammuz 5545 (23 June 1785), at about ninety, and was buried in the city's Jewish cemetery.