Muhammad ibn al-Hasan al-Tusi known as Nasir al-Din Tusi was one of the greatest scientists of medieval Islam. He is often considered the creator of trigonometry as a mathematical discipline in its own right.

He set up an observatory at Maragha (the modern Maragheh) in 1259 where he compiled a star catalog and tracked planetary motions with large quadrants. The resulting tables, published in 1272, remained in use until the time of Copernicus. As well as astronomy, al-Tusi made major contributions to many other areas of science including mathematics and biology.

Tusi acquired the honorific title of Khwaja (distinguished scholar and the teacher) in his lifetime. After his death, his influence continued in fields as diverse as ethics, philosophy, mathematics, logic, and astronomy, and he came to be referred to as used al-Bashar (teacher of mankind) and al-mu‘allim al-thalith (the third teacher, that is, after Aristotle and al-Farabi).

A 60-km diameter lunar crater located on the southern hemisphere of the moon is named after him as "Nasreddin". A minor planet 10269 Tusi discovered by Soviet astronomer Nikolai Stepanovich Chernykh in 1979 is named after him. The set of three commemorative stamps was issued on the 700th anniversary of his death. They depict al-Tusi’s tomb at Maragheh; an astrolabe, an Arabic star-sighting device about which he wrote a treatise; and a supposed representation of the man himself.

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