Ras Ajdir, alternatively Ras Jdir or Ras Ejder (Arabic: راس اجدير), is a small coastal town on the border of Tunisia and Libya and Libya's most northerly point.

It is the site of an experimental station for wind and solar power generation for desalination.

The town is a major transport hub and border crossing, for trade by road between Tunisia and Libya. From 15 February – 15 March 2007, 21,758 foreigners entered and 8,112 left through Ras Ajdir.

Ras Ajdir is a likely border station on the new Libyan Railways line, which is under construction in 2007. An agreement has been signed for a link to Tunisian Railways. The nearest Tunisian railhead, albeit of 1,000 mm (3 ft 3+3⁄8 in) guage, is at Gabès.

In 2011, during the Libyan Civil War, rebel forces attempted to take control of the crossing from loyalist forces. On 27 August, the border town was secured by the National Transitional Council forces.

• Railway stations in Libya

As of 2019, the population of the small coastal town of Ra's Ajdir is 6,469 people consisting of 6,023 Libyans, 306 Tunisians, 87 Algerians, 31 Italians, 9 Chadians, 7 Egyptians, and 6 Maltese.