An Nafud or Al-Nefud or The Nefud (Arabic: صحراء النفود, romanized: ṣahrā' an-Nafūd) is a desert in the northern part of the Arabian Peninsula at 28.30°N 41.00°E / 28.30; 41.00, occupying a great oval depression. It is 290 kilometres (180 mi) long and 225 kilometres (140 mi) wide, with an area of 103,600 square kilometres (40,000 sq mi).

The Nafud is an erg, a desert region located in north-central Saudi Arabia. It is noted for its sudden violent winds, which account for the large crescent-shaped dunes. The sand in the Nafud is a brick-reddish color. Rain comes once or twice a year. In some lowland areas, namely those near the Hejaz Mountains, there are oases where dates, vegetables, barley, and fruits are grown. The Nefud is connected to the Rub' al Khali by the Dahna, a corridor of gravel plains and sand dunes, 800 mi (1,287 km) long and 15 to 50 miles (24.1 to 80.5 km) wide.

During the Arab Revolt in 1917, forces led by Auda ibu Tayi attacked the Turkish-held coastal town of Aqaba on its poorly defended eastern flank. The approach was via long and wide desert route, passing close to the edge of the Nafud. Col. T. E. Lawrence asked Auda ibu Tayi to allow their group to stray from their course into the Nafud. Auda refused, because it was unnecessary. Their harsh transit did not include entering the Nafud, as is depicted in the film Lawrence of Arabia.

The discovery of an 85,000-year-old fossilised human finger in An Nafud in 2016 by Dr Mathieu Duval of Griffith University provided the earliest evidence of modern humans outside Africa and the Levant.