Rabbi Avraham ben HaRambam, also called "the Chassid" and "the Nagid", was born on 28 Sivan 4946 (1186) in Fustat, Old Cairo, when his father, Maimonides, was fifty-one. He studied under his father and became his closest confidant.

When the Rambam passed away in 1204, he succeeded him, at only eighteen, as Nagid, head of Egyptian Jewry, a position he held for about thirty years. A physician, he served as personal doctor to the Ayyubid sultan al-Malik al-Kamil and directed the public hospital in Cairo.

He introduced new practices in the synagogue, including additional prostrations and pietistic customs. These reforms met opposition from those loyal to the customs of the Land of Israel, and the dispute was brought before the sultan around 1232-1237.

Works: Kifayat al-Abidin (HaMaspik LeOvdei Hashem), a comprehensive Judeo-Arabic guide to the spiritual life, much of which is lost; a Torah commentary in Arabic, surviving for Genesis and Exodus; Milchamot Hashem, in defense of his father's thought; responsa, including the collection Birkat Avraham; and a commentary on the Talmud.

He passed away in Fustat on 18 Kislev 4998 (7 December 1237), at about fifty-one. His son, Rabbi David HaNagid, succeeded him as head of Egyptian Jewry; another son, Rabbi Ovadiah, is also known.