Abul-Hasan Kūshyār ibn Labbān ibn Bashahri Gilani (971 - 1029), also known as Kūshyār Gīlānī, was a Persian mathematician, geographer and astronomer from Jilan (now Gilan in current Iran).
His first job was probably Kushyar ibn Labban at the beginning of the 11th century. That work was a major evolution in the theory of goniometry. An example: he continued the investigations of Abul Wáfa and devoted much space to research in his side (a set of tables with goniometric numbers) or az-Zīj al-Jamī Wal-Baligh ("The Understandable and Conscious Tables"), which contain the new value of the planetary heights, which were observed by al-Battani.
The tables or tablets were translated into Persian before the end of the 11th century. He also wrote an astrological introduction and an arithmetic dissertation (still existing in Hebrew).
He was the teacher of Ahmad Nasawi. One believes he died in Baghdad.
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