Muslim Berber movement that developed into the leading political power in North Africa and Spain in the 12^th and 13^th century. Their teachings were based upon Ibn Tumart's interpretation of Islam, and their success was not only a result of their own power, as much as it was the downfall of the preceding Almoravid empire.
The central core of the Almohad movement – it could be called a rebellion against the Almoravids, actually – was the opposition against the position of the leaders of Almoravids as jurists. While large parts of their theology was rather unclear, one principle stood out: Tawhid, the uniqueness of God.
All through their 122 years of forming an empire, the Almohads were based upon a ruling elite, coming from the Masmuda tribe. This elite came from the founders of the Almohads, and continued by their decendants. However, the puritanical ideas of the founder Ibn Toumart, did not last long. Already his successor, Abdu l-Mu'min excelled in building expensive palaces and monuments, rich on ornamentation. Famous Moroccan structures, like the Kutubiyya mosque in Marrakech and the old mosque in Taza are from his period in power.
The Almohad crusade to purify Islam did not succeed as it was intended. Traditional Islam as Ibn Tumard perceived it, was equally dilluted by mystical movements of Sufism as well as the philosophical schools of Ibn Tufayl and Averröes as before.

Chronlogical dates
1117: Ibn Tumart returns to Morocco after performing hajj. He calls for a return to the principles of Islam: the Koran and the traditions of the prophet Muhammad.
1121: Ibn Tumart declares himself Mahdi.
1122: Ibn Tumert flees Marrakech, as he realizes that his life is in danger.
1124: A small Berber state grows up around the village of Tin Mal in the High Atlas Mountains (centre of what is today's Morocco), where Ibn Tumert has installed himself.
1130: Ibn Tumert dies, and is succeeded by Abdu l-Mu'min.
1147: The Almohad leader Abdu l-Mu'min conquers Marrakech, and brings and end to Almoravid rule. Now, the Almohads suddenly found themselves in control over northwestern Maghreb, but Spain was still outside their control.
1154: al-Mu'min secures control over southern Spain and Portugal.
1172: The Almohad caliph Abu Yaqub Yusuf forces Sevilla to surrender. Following this, more Spanish Muslim states are forced under Almohad control.
1212: With the Battle of Las Navas de Tolosa, the Almohad forces are seriously defeated by a Christian coalition from Leon, Navarra and Aragon. With this, the Almohads were forced back to Africa.
1236: Tunis is lost to the Hafsids.
1239: Tlemcen is lost to Abdu l-Wadid.
1269: The last Almohad stronghold, Marrakech, is conquered by the Merenids. This was the end of the Almohad empire.