The Trans-Sahara Highway is a proposed transnational highway project to pave, improve and ease border formalities on an existing trade route running north–south across the Sahara Desert. It runs between North Africa bordered by the Mediterranean Sea in the north and West Africa bordered by the Atlantic Ocean in the south, from Algiers in Algeria to Lagos in Nigeria, giving it the alternative names of the Algiers-Lagos Highway or Lagos-Algiers Highway.

The Trans-Sahara Highway is one of the oldest transnational highways in Africa and one of the most complete, having been proposed in 1962, with construction of sections in the Sahara starting in the 1970s. Its central section is still little-used though, and still requires special vehicles and precautions to be taken to survive the harsh environment and climate of the center of the desert.