Abu cAbd al-Rahman Muhammad b. al-Husayn al-Sulami (d.412/1021) lived in the 3rd and 4th century AH / 9th and 10th century CE. He was born in the city of Nishapur, one of the most renowned cities in the Islamic world. He was part of a line of earlier Sufi figures who attempted to defend the cardinal tenets of Sufism from accusations of heresy. However al-Sulami's surpassed his predecessors by amassing a corpus of antecedent mystical dicta from the architects of Islamic mysticism and substantiating them with transmission channels (isnad) or grounding them in a core teaching of the Prophet Muhammad. This study demonstrates that al-Sulami was an accomplished mystic. It outlines his life and times and surveys in full all his works as far as they can be identified. Moreover, the important sources that shaped the development and impression of his thinking and modality of transforming the ego-self (nafs) are presented in detail bringing together earlier and current academic scholarship on him.