The Libu (, R'bw, Ribou, Labu) were an Ancient Libyan tribe of an Amazigh origin, from which the name Libya derives.
Their occupation of Ancient Libya is first attested in Egyptian language texts from the New Kingdom, especially from the Ramesside Period. The earliest occurrence is in a Ramesses II inscription. There were no vowels in the Egyptian script. The name Libu is written as LBW or RBW in Egyptian hieroglyphs. In the Great Karnak Inscription Merneptah describes how hostilities between Egypt and Libya broke out and how the Libyans were defeated.Ramesses III defeated the Libyans in the 5th year of his reign, but six years later the Libyans joined the Meshwesh and invaded the western Delta and were defeated again.Libu appears as an ethnic name on the Merneptah Stele, also known as the Israel Stele.
This name Libu was taken over by the Greeks of Cyrenaica, who co-existed with them. Geographically, the name of this tribe was adopted by the Greeks for "Cyrenaica" as well as for northwestern Africa in general.
In the neo-Punic inscriptions, Libu was written as Lby for the masculine noun, and Lbt for the feminine noun of Libyan. The name supposedly was used as an ethnic name in those inscriptions.