Ulugh Beg (Uzbek: Mirzo Ulug'bek, Chagatai: الغبیگ Ulug Beg; real name: میرزا محمد طاراغایای بن شاه رخ – Mīrzā Muhammad Ṭaragay bin Shāh Rukh; 22 March 1394 – 27 October 1449), the 4th sultan of the Timurid Empire, was a Turkic mathematician and astronomer.
Ulugh Beg is known for his work in fields of mathematics related to astronomy, such as trigonometry and spherical geometry; he also stands out for his general interest in the arts and intellectual activities. He is thought to have known Arabic, Persian, Chagatai Turkic, and Mongolian, as well as Chinese to a limited degree. During his reign (first as governor, then effectively as ruler), thanks to the interest and patronage he showed, the Timurid Empire reached the peak of the cultural flowering called the Timurid Renaissance. Samarkand was conquered by his father Shahrukh and given to Ulugh Beg.
Between 1424 and 1429, Ulugh Beg had the Ulugh Beg Observatory built in Samarkand. This structure was regarded by the scholars of the period as one of the most distinguished observatories of the Islamic world and the largest in Central Asia. Thanks to these works, Ulugh Beg has been assessed by many researchers as the most important observational astronomer of the 15th century. Moreover, between 1417 and 1420 he had the Ulugh Beg Madrasa built in Samarkand and Bukhara, transforming these cities into important centers of learning and culture in Central Asia.
By contrast, Ulugh Beg's scientific competence was not matched by his administrative skills. Throughout his short reign he failed to consolidate his authority. Taking advantage of this situation, he was deposed by rival powers—among them his own family—and was finally killed.
His father was Shahrukh, the younger son of Timur, and his mother was Gawhar Shad. He was born in 1394 in the city of Soltaniyeh in Azerbaijan. His real name was Muhammad Taragay, but because he was beloved by Timur he came to be known by the title "Ulugh Beg," the Turkic equivalent of the Timurid "emir-i kabir" (great emir). Between 1394 and 1405 he studied, in addition to the religious sciences, logic, mathematics, and hay'a (astronomy) at the court. In 1404 he was married by Timur to Öge Begüm (Öge Biki), the daughter of Muhammad Sultan. He took part in the campaign Timur was to carry out against China. However, upon Timur's death at Otrar on 18 February 1405, he set out to return to Samarkand together with his corpse. Although Timur had, before his death, chosen his grandson Pir Muhammad as his heir, Khalil Sultan, another of Timur's grandsons, began to lay claim to the throne. When the defenders of Samarkand would not let Ulugh Beg and the emirs accompanying him into the city, he was forced to move on to Bukhara. When his life was no longer safe in Bukhara either, he secretly fled to Herat, where his father Shahrukh was. In 1406, at the head of the armies of his father and his cousin Pir Muhammad, he confronted Sultan Khalil in the vicinity of the Oxus (Ceyhun). However, since Sultan Khalil prevailed in the ensuing battle, he was forced to flee to Herat. In 1409, Shahrukh captured Sultan Khalil and gained control of Samarkand. Ulugh Beg then became ruler of that place under the supervision of Emir Shah Malik. Afterward, with the suppression of the revolt of Emir Nureddin and Emir Shah Malik's becoming governor of Herat, he began to rule single-handedly in the Transoxiana (Mâverâünnehir) region centered on Samarkand.