Oxynoe olivacea is a species of small green bubble snail or sea slug, a marine gastropod mollusk in the family Oxynoidae.

Despite a superficial resemblance, this is not a nudibranch, it is a sacoglossan, and like other Oxynoe species, it has a small, fragile, bubble-shaped shell.

Color above clear green, the borders of the foot and pleuropodial lobes, and ends of the tentacles margined with alternating spots of pale red and blue-black.

The columellar margin is with a very thin film of callus above, concave below, acute, forming an open spiral through which the interior of the whorls may be seen from the base.

Color is uniform glassy white, with a thin transparent and shining, very light yellow cuticle.