Rabi`ah ibn Nizar (Arabic: ربيعة) is the patriarch of one of two main branches of the "North Arabian" (Adnanite) tribes, the other branch being founded by Mudhar.
According to the classical Arab genealogists, the following are the important branches of Rabi`ah:
Like the rest of the Adnanite Arabs, legend has it that Rabi`ah's original homelands were in the Tihamah region of western Arabia, from which Rabi`ah migrated northwards and eastwards. Abd al-Qays were one of the inhabitants of the region of Eastern Arabia, including the modern-day islands of Bahrain, and were mostly sedentary.
Bakr's lands stretched from al-Yamama (the region around modern-day Riyadh) to northwestern Mesopotamia. The main body of the tribe was bedouin, but a powerful and autonomous sedentary sub-tribe of Bakr also resided in al-Yamama, the Bani Hanifa.
Taghlib resided on the eastern banks of the Euphrates, and al-Nammir are said to have been their clients. Anz inhabited southern Arabia, and are said to have been decimated by the plague in the 13th century, though a tribe named "Rabi`ah" in modern-day 'Asir is said to be its descendant.
Anazzah was divided into a sedentary section in southern Yamama and a bedouin section further north.
Abd al-Qays, Taghlib, al-Nammir, and some sections of Bakr were mostly Christian before Islam, with Taghlib remaining a Christian tribe for some time afterwards as well. Anazzah and Bakr are said to have worshiped an idol by the name of al-Sa'eer.