He was born around 858 in Tur, Iran to a wool seller. Al-Hallaj's grandfather may have been a Zoroastrian. His father lived a simple life, and this form of lifestyle greatly interested the young al-Hallaj. As a youngster he memorized the Quran and would often retreat from worldly pursuits to join other mystics in study.
Al-Hallaj would later marry and make a pilgrammige to Mecca. After his trip to the holy city, he traveled extensively and wrote and taught along the way. He travelled as far as India and Central Asia gaining many followers, many of which accompanied him on his second and trips to Mecca. After this period of travel, he settled down in the Abbasid capital of Baghdad.
Among other Sufis, Al-Hallaj was an anomaly, many sufi masters felt that it was inappropriate to share mysticism with the masses, yet Al-Hallaj openly did so in his writings and through his teachings. He would begin to make enemies, and the rulers saw him as a threat. This was exacerbated by times when he would fall into trances which he attributed to being in the presence of God. During one of these trances, he would utter Ana al-Haqq, meaning that "I am the Truth", which was taken to mean that he was claiming to be God, as Al-Haqq is one of the Ninety Nine Names of Allah.
This utterance would lead him to a long trial, and subsequent imprisonment for eleven years in a Baghdad jail. In the end, he would be tortured and publicly crucified by the Abbasid rulers for what they deemed as a heresy. Many accounts tell of Al-Hallaj's calm demeanor even while he was being tortured, and indicate that he forgave those who had executed him. He died on March 26, 922.
His writings are very important to only Sufis, but to all Muslims. His example is seen by some as one that should be emulated, especially his calm demeanor in the face of torture and his forgiving of his tormentors. Others continue to see him as a heretic.