(Arabic, contraction of al-Khaḍir, “the Green One”), a legendary Islāmic (Islām) figure endowed with immortal life who became a popular saint, especially among sailors and Ṣūfīs (Muslim mystics).

The cycle of myths and stories surrounding al-Khiḍr originated in a vague narrative in the Qurʾān (18:60–82) that describes the long and arduous journey of Mūsā (Moses) and his servant to the “meeting of the two seas.” In the course of their travels, they lose a fish they had taken with them; a man of God appears, offering to help them in their search for the fish but performs seemingly senseless deeds along the way—he sinks a boat, kills a young man, then restores a wall in a city hostile to them. Mūsā questions what the man has done and receives a satisfactory explanation for everything; but by questioning, Mūsā forfeits the man's patronage. Arab commentators elaborated and embellished the Qurʾānic story and named the “man of God” Khiḍr, claiming that he turned green as he dived into the spring of life, though variant interpretations identify Khiḍr with the vegetable world.

On a popular level, Khiḍr has been given a name (most frequently Balyā ibn Malkān), many different genealogies, and dates that have made him a contemporary of Abraham or Alexander. Khiḍr's immortality and ability to assume a variety of local characteristics probably account for his widespread popularity among Arabs, Turks, Iranians, and other Muslims, despite orthodox Islāmic opposition. In Syria, Khiḍr became partially identified with St. George, who, according to a local tradition, is of Syrian birth; in India and Pakistan, Khiḍr is identified with a water deity (Khwādja Khiḍr) specializing in the protection of mariners and river travelers; and, among the Ṣūfīs, he is associated with their founders, who were often endowed with holiness and sainthood.