Isidore of Miletus (Ισίδωρος ο Μιλήσιος,in Greek) was one of the two Greek architects (the other being Anthemius of Tralles) who designed the church of Hagia Sophia in Constantinople (what is today Istanbul in Turkey).
The Emperor Justinian I decided to rebuild the 4th century basilica in Constantinople which was destroyed during the Nika riots of 532. He employed Isidore of Miletus along with Anthemius of Tralles.
Isidore of Miletus had earlier taught physics in Alexandria, Egypt and then later at Constantinople, and had written a commentary on earlier books on building. He had also collected and publicized the writings of Eutocius, which were commentaries on the mathematics of Archimedes and Apollonius, and consequently helped to revive interest in their works. Through this act, these most important of writings have been preserved and passed on to future generations. Furthermore, he was also an able mathematician, to him we owe the Tsquare and string construction of a parabola and possibly also the apocryphal Book XV of Euclid's Elements.^{[1]}

