ABSTRACT: Radar imagery of the Sahara of Egypt and eastern Libya has dramatically changed previous concepts in regard to long term aridity of this region, revealing an extensive network of buried fluvial channels documenting the river systems that developed in the proto-Sahara during the Late Paleogene and Neogene, following the early Eocene regression of the Mediterranean Sea, and prior to Pleistocene aridification. The fall in base level associated with the end-Miocene Messinian desiccation of the Mediterranean led to deep down-cutting and extension of river systems throughout much of North Africa and South Europe. The deep, infilled canyons beneath the modern Rhone and Nile are well known, but the radar imagery identifies other deep canyons under the North African Sahara that are now invisible. In eastern Libya, drainage from Serir Tebisti (Tebisti Massif) into the Mediterranean via the Sirt Basin was channeled by two main rivers, the Sahabi in the west and the Kufra in the east; these were subsequently united in the Early Pliocene when the latter captured the former. The Gilf River was another important channel that drained north from the Uweinat–Gilf highland in southwest Egypt, in a system that may have been connected with the Kufra during the Neogene and enabling fish to move from the presently isolated Chad Basin to northern Libya and Egypt. The interplay of these north-flowing rivers and the constant northward retreat of the Mediterranean shoreline from Oligocene onward resulted in deposits of fluvial and marine sedimentation in every possible combinaton that have been described by many authors in the region between the Tebisti and the present Mediterranean shoreline. Prior to the establishment of the Nile, a southwestward drainage, the Qena River, was initiated by Oligocene uplift and lateral faulting along the Red Sea shoulder of the East African Rift. This river discharged into a distributive network known as the Radar Rivers near latitude 23°30’N in the Southwestern Desert. It has been suggested that waters from the Qena River continued to flow southwestward to the Atlantic Ocean, in what is known as Trans African Drainage System (TADS).