Zīj-i Sulṭānī (Persian: زیجِ سلطانی) is a Zij astronomical table and star catalogue that was published by Ulugh Beg in 1438–1439.
The Zij-i-Sultani was not surpassed in accuracy until the work of Taqi ad-Din and Tycho Brahe in the 16th century.
This catalogue, one of the most original of the Middle Ages, was edited by Thomas Hyde at Oxford in 1665 under the title Jadāvil-i Mavāzi' S̱avābit, sive, Tabulae Long.
Stellarum Fixarum ex Observatione Ulugh Beighi, by Gregory Sharpe in 1767, and in 1843 by Francis Baily in Vol.
This value was improved by 28s, 88 years later in 1525 by Nicolaus Copernicus (1473–1543), who appealed to the estimation of Thābit ibn Qurra (826–901), which was accurate to +2s.