Claudius Ptolemaeus (Greek: Κλαύδιος Πτολεμαῖος; ca. 90 – ca. 168 AD), known in English as Ptolemy, was a Greek mathematician, geographer, astronomer, and astrologer who lived in Roman Egypt. Although no description of his family background or physical appearance exists, it is likely he was born in Egypt, probably in or near Alexandria.
Ptolemy was the author of several scientific treatises, three of which would be of continuing importance to later Islamic and European science. The first is the astronomical treatise that is now known as the Almagest (in Greek Η μεγάλη Σύνταξις, "The Great Treatise"). The second is the Geography, which is a thorough discussion of the geographic knowledge of the Greco-Roman world. The third is the astrological treatise known as the Tetrabiblos ("Four books") in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day.