The Banu Hilal were a confederation of Arabian Bedouin

Bedouin

The Bedouin are a part of a predominantly desert-dwelling Arab ethnic group traditionally divided into tribes or clans, known in Arabic as ..-Etymology:...

 tribes that migrated from Upper Egypt into North Africa

North Africa

North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...

 in the 11th century, having been sent by the Fatimid

Fatimid

The Fatimid Islamic Caliphate or al-Fāṭimiyyūn was a Berber Shia Muslim caliphate first centered in Tunisia and later in Egypt that ruled over varying areas of the Maghreb, Sudan, Sicily, the Levant, and Hijaz from 5 January 909 to 1171.The caliphate was ruled by the Fatimids, who established the...

s to punish the Zirid

Zirid

The Zirid dynasty were a Sanhadja Berber dynasty, originating in modern Algeria, initially on behalf of the Fatimids, for about two centuries, until weakened by the Banu Hilal and finally destroyed by the Almohads. Their capital was Kairouan...

s for abandoning Shiism. Other authors suggest that the tribes left the grasslands on the upper Nile

Nile

The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

 because of environmental degradation

Environmental degradation

Environmental degradation is the deterioration of the environment through depletion of resources such as air, water and soil; the destruction of ecosystems and the extinction of wildlife...

 accompanying the Medieval Warm Period

Medieval Warm Period

The Medieval Warm Period , Medieval Climate Optimum, or Medieval Climatic Anomaly was a time of warm climate in the North Atlantic region, that may also have been related to other climate events around the world during that time, including in China, New Zealand, and other countries lasting from...

. The Banu Hilal quickly defeated the Zirids and deeply weakened the neighboring Hammadid

Hammadid

The Hammadids were a Berber dynasty who ruled an area roughly corresponding to north-eastern modern Algeria for about a century and a half , until they were destroyed by the Almohads...

s. Their influx was a major factor in the linguistic, cultural and ethnic Arabization

Arabization

Arabization or Arabisation describes a growing cultural influence on a non-Arab area that gradually changes into one that speaks Arabic and/or incorporates Arab culture...

 of the Maghreb

Maghreb

The Maghreb is the region of Northwest Africa, west of Egypt. It includes five countries: Morocco, Algeria, Tunisia, Libya, and Mauritania and the disputed territory of Western Sahara...

, and in the spread of nomadism in areas where agriculture

Agriculture

Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 had previously been dominant. Ibn Khaldun

Ibn Khaldun

Ibn Khaldūn or Ibn Khaldoun was an Arab Tunisian historiographer and historian who is often viewed as one of the forerunners of modern historiography, sociology and economics...

 noted that the lands ravaged by Banu Hilal invaders had become completely arid desert.

They were led by Abu Zayd al-Hilali

Abu Zayd al-Hilali

Abu Zayd Ibn Rizq Al-Hilali was a 11th century Arab leader and hero of the 'Amirid tribe of Banu Hilal.On the orders of the Ismaili Fatimid caliph, Abu Zayd moved his tribe to Tunisia via Egypt to punish the Zirids for adopting Sunniism. The Banu Hilali weakened largely the Zirid state and sacked...

. Their story is recounted in fictionalized form in Taghribat Bani Hilal

Taghribat Bani Hilal

Taghribat Bani Hilal is an Arabic epic recounting the Banu Hilal's journey from Najd to Tunisia via Egypt and conquest of the latter. It is built around historical events that took place in the 11th century...

.

Their "saga" is still recounted in form of poetry in Algeria, Tunisia and Egypt: Djezia and Dhieb bin Ghanim opposed
to the Zenati Khalifa.