Dryas octopetala, the mountain avens, eightpetal mountain-avens, white dryas or white dryad, is an Arctic–alpine flowering plant in the family Rosaceae. It is a small prostrate evergreen subshrub forming large colonies. The specific epithet octopetala derives from Greek octo 'eight' and petalon 'petal', referring to the eight petals of the flower, an unusual number in the Rosaceae, where five is the normal number. However, flowers with up to 16 petals also occur naturally.

Rosaceae, the rose family, is a medium-sized family of flowering plants that includes 4,828 known species in 91 genera.