Jahm ibn Ṣafwān (جَهْم بن صَفْوان) was an Islamic theologian who attached himself to Al-Harith ibn Surayj, a dissident in Khurasan towards the end of the Umayyad period, and who was put to death in 746 by Salm b. Aḥwaz.
Of possible Persian descent, he was born in Kufa, but settled down in Khurāsān in Tirmidh. He learned under al-Ja'd b. Dirham, a theologian from Harran in Syria. al-Ja'd b. Dirham was a teacher of the last Umayyad caliph, Marwan II, and is described as a Dahrī and Zindīq. He was the first Muslim reported to have spoken about the createdness of the Qurʾān and reject Abraham's friendship with God and Moses' speaking to Him. The name of Jahm b. Ṣafwān would later be ascribed - possibly spuriously - to the theological movement known as the Jahmiyya (see: Jahmites).
Jahm worked as the assistant to Al-Harith ibn Surayj during the latter's revolt against the Umayyad governor Nasr ibn Sayyar. Jahm was killed during the first attempt to take Merv in 746, though the revolt greatly weakened Umayyad power and indirectly contributed to the success of the Abbasid Revolution.
Establishing the positive content of Jahm's doctrines is difficult, as they are reproduced (in an abbreviated form) only in later polemical works that are impossible to verify. However, it is said that he taught that only a few attributes can be predicated to God, such as creation, divine power and action, whilst others such as speech cannot. Therefore, he believed that it was wrong to talk about the eternal word of the Qur'an, since God (according to Jahm) is not a speaker in the first place.
Jahm was a proponent of extreme determinism, according to which a man acts only metaphorically in the same way in which the sun is said to set: according to Jahm, this is a linguistic convention rather than an accurate description, as it is actually God that makes the sun set.
Jahm's doctrines about God and His Attributes were taken up in criticisms of the Mu'tazila, who were sometimes called Jahmites by their adversaries. The Mu'tazila believed that the Qur'ān is created, a tenet wherein they agreed with Jahm's recorded view.
Jahm b. Ṣafwān was heavily criticized by later scholars for his theological teachings. Many Hadith scholars wrote refutations of Jahm bin Ṣafwān's doctrines, particularly Ahmad ibn Hanbal, al-Bukhari, and al-Darimi. The latter also wrote a large refutation of a prominent Jahmite by the name of Bishr b. Ghiyāt al-Mārisî wherein he declared him a Kafir (an unbeliever).
Jahm left no writings, but many Muslim scholars wrote about his doctrines and a few modern scholars have written studies of him.