Claudius Ptolemy (Κλαύδιος Πτολεμαῖος, Klaudios Ptolemaios, Claudius Ptolemaeus; c. AD 90 – c. 168) was a Greco-Egyptian writer of Alexandria, known as a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. The Almagest is the only surviving comprehensive ancient treatise on astronomy.