Shaykhism (Arabic: الشيخية, romanized: al-Shaykhiyya) is a term used by Shia Muslims for the followers of Shaykh Ahmad in early 19th-century Qajar Iran. While grounded in traditional Twelver Shiʻi doctrine, Shaykhism diverged from the Usuli school in its interpretation of key ideas such as the nature of the end times and the day of resurrection, the source of jurisprudential authority, and the proper hermeneutic to be employed in interpreting prophecy through the mystical writings of the Twelver Imams. These divergences resulted in controversy and ongoing accusations of heresy from Usulis and Akhbaris.

It has been described as a mystical strand of Twelver Shi'a Islam. As of 2001^[update], there remained a following in Iran, Iraq, Saudi Arabia, Kuwait and Pakistan.

The primary force behind Ahmad's teachings is the belief in the occultation of the Twelfth Imam. Believers in this doctrine, hold that the last divine ordained leader, or Imam, lives in occultation and will reappear as the promised Mahdi. Following the Mahdi's appearance, Ahmad teaches that the Imam Hussain ibn Ali will return to re-conquer the world and that Ali and Muhammad will kill Satan then Hussain will rule over the World for 50,000 years. Al Raj'a (meaning "the return" in English) was heavily emphasized by Ahmad and is more important in Shaykhism than in the Usuli school of Islam.

Shaykh Ahmad's perspectives on accepted Islamic doctrines diverged in several areas, most notably on his mystical interpretation of prophesy. The sun, moon and stars of the Qurʼan's eschatological surahs are seen as allegorical, similar to Ismaili doctrine, where common Muslim interpretation is that events involving celestial bodies will happen literally at the Day of Judgment.

In an effort to "harmonize reason and religion" and "explain some doctrines of Islam that appear contrary to reason" and the laws of the natural world, Shaykh Ahmad, postulated an intermediary world between the physical and spiritual worlds that he called hurqalya. Everything in the physical world would have counterparts in hurqalya, and events and concepts of Islamic doctrine that did not make sense in the physical world -- heaven, hell, resurrection from the dead, Muhammad's Isra' and Mi'raj, the long life of the Twelfth Imam and the two cities "he is supposed to live" in, Jabulqa and Jabulsa -- all would exist in the realm of hurqalya. Consequently, everyone would have two bodies, one in the natural world and one in hurqalya. Shaykhism teaches that Zuhūr and Raj'a are both in Hurqalya then comes the World of Qiyamah which is mixture between the Physical World and Hurqalya. It was this concept of hurqalya, "more than anything else" that led to Shaykh Ahmad's conflict with the ulama.

In other writings, Shaykh Ahmad synthesizes rather dramatic descriptions of the origin of the prophets, the primal word, and other religious themes through allusions and mystical language. Much of this language is oriented around trees, specifically the primal universal tree of Eden, described in Jewish scripture as being two trees. This primal tree is, in some ways, the universal spirit of the prophets themselves:

The symbol of the preexistent tree appears elsewhere in Shaykh Ahmad's writings. He says, for instance, that Muhammad and the Imams exist both on the level of unconstrained being or preexistence, wherein they are the Complete Word and the Most Perfect Man, and on the level of constrained being. On this second, limited plane, the cloud of the divine Will subsists and from it emanates the Primal Water that irrigates the barren earth of matter and of elements. Although the divine Will remains unconstrained in essential being, its manifest aspect has now entered into limited being. When God poured down from the clouds of Will on the barren earth, he thereby sent down this water and it mixed with the fallow soil. In the garden of the heaven known as as-Saqurah, the Tree of Eternity arose, and the Holy Spirit or Universal Intellect, the first branch that grew upon it, is the first creation among the worlds.

Shaykh Ahmad, at about age forty, began to study in earnest in the Shiʻa centres of religious scholarship such as Karbala and Najaf. He attained sufficient recognition in such circles to be declared a mujtahid, an interpreter of Islamic Law. He contended with Sufi and Neo-Platonist scholars, and attained a positive reputation among their detractors. He declared that all knowledge and sciences were contained (in essential form) within the Qurʼan, and that to excel in the sciences, all knowledge must be gleaned from the Qurʼan. His leadership style and approach to interpretation draw both on traditional and theosophical methods, attempting to harmonize these two streams of Shiʻia thought in unprecedented ways, and emphasizing the validity of intuitive knowledge for religious thought. Rather than relying entirely on Ijtihad, or independent rational justification, Shakyh Ahmad claimed to derive direct guidance from the Imams. Relying entirely on individual justification for religious guidance had, he suggested, led to the introduction into Shiʻa belief of erroneous views of particular scholars. By emphasizing the role of a charismatic leader whose work was suggested to share in the infallibility of the Imams, Shakyh Ahmad suggested that the diversity of rulings promoted by the ulama could be replaced with a singular set of doctrines-this view would later find widespread support in the Ayatollah system of modern Usulism. His views resulted in his denunciation by several learned clerics, and he engaged in many debates before moving on to Persia where he settled for a time in the province of Yazd. It was in Isfahan that most of this was written.^{[citation needed]}