Abul Hassan Ali Ibn Usman al-Jullabi al-Hajweri al-Ghaznawi or Abul Hassan Ali Hajweri, also known as Data Ganj Bakhsh or Data Sahib, was a Persian Sufi and scholar during the 11th century. He significantly contributed to the spreading of Islam in South Asia.
He was born in Ghazna (in present day Afghanistan) in the beginning of Ghaznavids period (around 990) and died in Lahore (in present day Punjab, Pakistan) in 1077 CE. His most famous work is The Kashf Al Mahjub ("Unveiling the Veiled") written in Persian language. The work debates Sufi doctrines of the past.
Hujwiri belonged to the Junaidia school of Sufism. These sufis followed Junaid Baghdadi of Baghdad. Hajwiri is also viewed as an important intercessor for many Sufis.
Hujwiri probably entered the Sufi path very early in his life and spent many years travelling to Iran, Iraq, Syria etc, during which he met several Sufi saints. He studied Sufism under Abu'l-Fadl Muhammad b. al-Hasan al-Khuttali through whom he is spiritually connected) with Junaid Baghdadi. He settled for some time in Iraq where he had a short experience with married life. Finally he was taken as a captive to Lahore, where he spent the rest of his life and compiled the major portion of his book, The Kashf Al Mahjub.