Agathodaemon of Alexandria (Ancient Greek: Ἀγαθοδαίμων Ἀλεξανδρεὺς, Agathodaímōn Alexandreùs) was a Greek or Hellenized Egyptian cartographer, presumably from Alexandria, Roman Egypt, during late Antiquity, likely in the 2nd century AD.
Agathodaemon is mentioned in some of the earliest manuscripts of Ptolemy's Geography:
The Ptolemy world map is a map of the world known to Greco-Roman societies in the 2nd century. It is based on the description contained in Ptolemy's book Geography, written c. 150. Based on an inscription in several of the earliest surviving manuscripts, it is traditionally credited to Agathodaemon of Alexandria.
Notable features of Ptolemy's map is the first use of longitudinal and latitudinal lines as well as specifying terrestrial locations by celestial observations. The Geography was translated from Greek into Arabic in the 9th century and played a role in the work of al-Khwārizmī before lapsing into obscurity. The idea of a global coordinate system revolutionized European geographical thought, however, and inspired more mathematical treatment of cartography.