The Fontaine de Vaucluse (French pronunciation: [fɔ̃tɛn də voklyz]) is a karst spring in the commune of Fontaine-de-Vaucluse, France.

The village in which the spring is located was called "Vallis Clausa" ("closed valley") in Latin because of its topographical position.

This karstification phenomenon acting on the surface of the impluvium, removes an annual volume of 45 cubic metres (1,600 cu ft) per square kilometre, which disappears after being dissolved in the water.

A legend tells that Saint Veranus, bishop of Cavaillon, rid the Sorgue of a horrible Drac, a devil or dragon, the Coulobre(fr).

The Coulobre, whose name could be derived from the Latin word coluber (snake), was a winged creature who lived in the Fontaine de Vaucluse.

[8] According to Albert Dauzat and Charles Rostaing, the Drac is a Ligurian divinity of tumultuous waters and the Coulobre owes its name to two Celto-Ligurian(fr) roots: Kal (stone) and Briga (hill).

This is the cliff overlooking the spring which still holds the Vache d'Or, the site of an ancient pastoral religion celebrating the strength and form of water and stone.

Dr. Henri Louis Joseph Ayme(fr) organized exploration of the basin and on 24 September 1938 Negri reached a depth of 27.5 metres (90 ft).

[12] In 2014 a virtual tour was created by the photographer Christoph Gerigk in collaboration with the Speleological Society of Fontaine de Vaucluse (SSFV) from 360° spherical panoramic views.

[13] Today, the joint efforts of geologists, hydrogeologists, hydrochemists and speleologists have made it possible to gain a better understanding of the functioning of this karst spring.

[15] The part of the reservoir that is accessible to speleologists exceeds a depth of −921 metres (−3,022 ft),[a] since it has been explored during a period of low water from several open cavities forming the karst system of the Souffleur hole of Saint-Christol, the "underground river of Albion".

With an average of 21 cubic metres (740 cu ft) per second, it yields seven times more than all the drinking water distributed in the department of Vaucluse.