Ouadane or Wādān (Arabic: وادان) is a small town in the desert region of central Mauritania, situated on the southern edge of the Adrar Plateau, 93 kilometres (58 mi) northeast of Chinguetti. The town was a staging post in the trans-Saharan trade and for caravans transporting slabs of salt from the mines at Idjil.

The old town, a World Heritage Site, though in ruins, is still substantially intact, while a small modern settlement lies outside its gate.

Ouadane is the closest town to the Richat Structure, a massive circular landmark visible from space.

The whole Ouadane commune has a total size of 118,210 square kilometres (45,640 sq mi), mostly consisting of desert. The main town is located in the south-west of the commune.

The early history of Ouadane is uncertain but it is possible that the town prospered from the trans-Saharan gold trade. In the middle of the 11th century, the Arabic geographer al-Bakri described a trans-Saharan route that ran between Tamdoult near Akka in Morocco to Aoudaghost on the southern edge of the Sahara. This route was used for the transport of gold during the time of the Ghana Empire. In his account al-Bakri mentioned a series of place names but these have not been identified and historians have suggested several possible routes. In 1961 the French historian Raymond Mauny proposed a route that passed through Ouadane but Suzanne Daveau later argued in favour of a more direct route that crossed the Adrar escarpment to the east of the town. The volume of caravan traffic would have declined from the beginning of the 13th century when the oasis town of Oualata located 360 kilometres (220 mi) to the east replaced Aoudaghost as the southern terminus of the trade route.

The first written reference to the town is in Portuguese by Ca' de Mosto in middle of the 15th century in a muddled account that confused the salt mines of Idjil with those of Taghaza. At about the same date Gomes Eanes de Zurara described Ouadane as the most important town of the Adrar region and the only one with a surrounding wall. Fifty years later Valentim Fernandes wrote a detailed account of the trade in slabs of salt from the Idjil mines and role of Ouadane as an entrepôt. He described Ouadane as a 'town' with a population of 400 inhabitants. By contrast Duarte Pacheco Pereira in his Esmeraldo de situ orbis (written in 1505-1508) described the town as having approximately "300 hearths" which would suggest between 1,500 and 1,800 people. The Idjil sebkha lies roughly 240 kilometres (150 mi) northwest of Ouadane, to the west of the town of Fderîck. The date when salt was first extracted from the sebkha is unknown. It is usually assumed that exploitation of the Idjil mines began after the mid 11th century as al-Bakri did not mention them. Instead he described a salt mine at a place that he called 'Tatantal'. Historians have usually assumed this corresponds to Tegahza but his description could possibly also apply to the mines at Idjil.

According to Pereira, in 1487 the Portuguese built an entrepôt in Ouadane in an attempt to gain access to the trans-Saharan gold, salt and slave trade. The entrepôt was probably short lived and is not mentioned in the detailed description provided by Fernandes.

In the 16th century the Moroccans made various attempts to take control of the trans-Saharan trade in salt and especially that in gold from the Sudan. They organised military expeditions to occupy Ouadane in 1543-44 and again in 1584. Then in 1585 they occupied Taghaza and finally in 1591 their victory in the Battle of Tondibi led to the collapse of the Songhay Empire.