Shi'i Islamic sect with much power from around 880 until around 1080, although it continued for still some time in Bahrain. The Qarmatians had a belief system that mixed elements from Islam, gnosticism and perhaps even Mandaism. The Qarmatians originate with Batiniya.
Through its short history, Qarmatianism was an arena for much speculations, and it would exercise much influence on other Islamic orientations.
Their society had many similarities with communism. The ideology was dominated by ideals of reason, tolerance and equality. Qarmatians groups based themselves on voluntary gifts from its members. All property inside the community was distributed evenly among all initiates.
The Qarmatians were organized as an esoteric society but not as a secret one. Their activities were visible to the public, and openly propagated. But you could become member only after an initiation. Initiates would pass through 7 degrees, similar to the system of Mithraism.
The Qarmatian world view was one where every phenomena repeated itself in cycles, where every incident was replayed over and over again. The Qarmatians claimed that the prophets and imams were sparks different from the blind matter. By losing the sense of individuality and gaining insight, were these sparks able to liberate themselves and gain divine identity.
Qarmatian groups formed an independent state in the region of the al-Hasa oasis of Arabia and in Bahrain. There were also strong groups of Qarmatians in Syria and Yemen.
The Qarmatians have been seen linked to the Nusayris, leading up to Alawitism, Alevism, Ahl-e Haqq and perhaps even Yazidism.
The origin of the name is most likely connected to the first important leader Hamdan Qarmat.

History
877: War of the Zanj, creating a reaction within the Shi'i groups.
890: Hamdan Qarmat forms a dar al-hijra east of Kufa, a closed and protected community.
899: Al-Hasa comes under control of the Qarmatian leader al-Jannabi, and is declared independent from the Abbasids of Baghdad. The capital was al-Mu'miniya (near modern Hufuf).
900: The Qarmatian uprising starts in the Syrian desert.
903: The leader of the Qarmatian uprising is captured and executed in Baghdad.
906: The Qarmatian uprising is finally suppressed.
10th century: The city of Kufa acked several times by the Qarmatians and is gradually destroyed before turning into nothing more than a village.
Oman is conquered by the Qarmatians.
930 January 12: Qarmatian leader Abu Tahir Sulayman sacks Mecca, and takes with him the Black Stone of the Ka'ba.
1077: The Qarmatian state of al-Hasa is overthrown. Qarmantians retain control over Bahrain.