Ulugh Bek (Uzbek: Muhammad Tarag'ay Ulug'bek; ???????? ??????? ???????; Persian: ????? ???? ???? ?? ????? ??????? - Mirza Muhammad Taraghay bin Shahrukh Ulug Bek) (22 March 1394 in Sultaniyeh (Persia) - 27 October; 1449 (Samarkand) was a Timurid ruler as well as an astronomer; mathematician and sultan.

His commonly-known name is not truly a personal name; but can be loosely translated as 'Great Ruler' and was the Turkic equivalent of Timur's Perso-Arabic title Amir-e Kabir. His real name was Mirza Mohammad Taraghay bin Shahrokh. Ulugh Beg was notable for his work in astronomy-related mathematics; such as trigonometry and spherical geometry. He built the great observatory in Samarkand; between 1424 and 1429.