Euclid (/ˈjuːklɪd/; Greek: Εὐκλείδης Eukleidēs Ancient Greek: [eu̯.klěː.dɛːs]; fl. 300 BC), sometimes called Euclid of Alexandria to distinguish him from Euclid of Megara, was a Greek mathematician, often referred to as the "Father of Geometry". He was active in Alexandria during the reign of Ptolemy I (323–283 BC).