Rabbi Avraham Danzig (ben Yehiel Michael, אברהם דנציג ;1820–1748) was a Posek ("decisor") and codifier, best known as the author of the works of Jewish law called "Chayei Adam" and "Chochmat Adam." He is sometimes referred to as "the Chayei Adam".
Rabbi Danzig was born in Danzig (Gdańsk), Poland (hence his name), in 1747 or 1748 into a prominent Rabbinic family. When he was fourteen his father sent him to study at the Prague yeshivah, after exacting a promise from him "that he would not mingle with the Moderns" who were then gradually coming into prominence through the influence of Moses Mendelssohn.
He studied in Prague for four years under Rabbi Yechezkel Landau and Rabbi Joseph Liebermann. He was then offered a position as Rabbi in Vilna, but declined, earning his livelihood as a merchant (frequenting the fairs of Leipzig and Königsberg - which are referenced in his writings). Only in his later years, and after having lost almost his entire fortune through the explosion of a powder-magazine, could he be induced to accept the position of dayan in Vilna, where he served until 1812. He died there on September 12, 1820.
Rabbi Danzig is one of three authorities on whom Rabbi Shlomo Ganzfried based his rulings in the Kitzur Shulchan Aruch.
Descendants today of Avraham Danzig include Rabbi Neil Danzig and Rabbi Joseph Meyer Danzig, son of Rabbi Avraham Mordechai Danzig, who was born in Jerusalem and named after his prominent ancestor.
Rabbi Danzig authored several important works, but he is especially known for Chayei Adam and Chochmaא Adam, his works of halacha covering the laws of the Shulchan Aruch dealing with everyday life.