The Berber religious movement and dynasty that ruled North Africa and Muslim Spain in the 12th–13th centuries, until its power in Iberia was broken at Las Navas de Tolosa.
The movement was founded by Ibn Tumart, a Masmuda Berber scholar who returned from the Islamic east preaching a rigorous doctrine of divine unity and denouncing the ruling Almoravids as lax. Proclaimed the infallible Mahdi by his followers around 1121, he organised a militant community in the High Atlas. After his death his disciple Abd al-Mu’min took the title of caliph, welded the Berber tribes into an army, and over two decades conquered all of Morocco, taking the Almoravid capital Marrakesh in 1147.
From the Maghreb the Almohads crossed into al-Andalus, absorbing the fragmented Muslim taifa states and confronting the advancing Christian kingdoms of Iberia.
Under Abd al-Mu’min’s successors the caliphate reached its height. Yaqub al-Mansur crushed the Castilians at Alarcos in 1195 and presided over a great flowering of architecture: the Giralda minaret in Seville, the Koutoubia in Marrakesh, and the unfinished Hassan Tower of Rabat all date from Almohad patronage, sharing a severe, geometric brick style. The court also protected philosophers, most famously Averroes (Ibn Rushd).
At its greatest extent the empire ran from the Atlantic coast of Morocco across North Africa and into southern Spain, the last great Berber empire to hold both shores of the strait.
The turning point came in 1212, when a crusading coalition of Castile, Aragon, and Navarre destroyed the army of the caliph Muhammad al-Nasir at Las Navas de Tolosa. The defeat shattered Almohad prestige and manpower in Iberia and opened al-Andalus to Christian conquest: Córdoba fell to Castile in 1236 and Seville in 1248.
In the Maghreb the caliphate fragmented as Berber rivals — the Marinids, Hafsids, and Zayyanids — carved up its lands, and the last Almohad caliph was killed at Marrakesh in 1269. Their fall reshaped the western Mediterranean, hastening both the Reconquista in Spain and the rise of new dynasties in North Africa.