Fontaine de Barenton, Medieval fountain in Paimpont Forest, France.

Fontaine de Barenton is a spring fountain arising from natural rock formations in Paimpont Forest, producing cold water that forms bubbles on the surface year-round. The spring lies within the woodland landscape and is accessible by marked walking paths.

The first text to mention the fountain is the Roman de Rou, an Old French poem by the Norman cleric Wace of Jersey, dated around 1160, which calls it Berenton and describes Bretons pouring its water on the stone to bring rain. Wace writes that he visited the site himself and found nothing. A quarter-century later Chrétien de Troyes used the fountain and its stone in Yvain ou le Chevalier au lion, tying it to the Arthurian legend.

The fountain appears in medieval literature, particularly in Chrétien de Troyes' story of the knight Yvain, who poured water on the stone to call forth storms. These literary connections have kept the site alive in popular imagination across the centuries.

The fountain is reached by a walking path from Folle Pensee parking area, requiring an average walk of about 3 kilometers. Access may be restricted on Thursdays during hunting season from September through March.

The water stays at about 10 °C all year and sometimes seems to boil, releasing large bubbles of pure nitrogen and carbon dioxide, especially in stormy weather. Red pebbles on the ground resemble embers, and morning mist can produce a spectre that locals attribute to King Solomon of Brittany.