Euphorbia melanadenia is a species of euphorb known by the common name red-gland spurge. It is native to the deserts and mountains of Baja California and southern California and Arizona, where it grows in dry, rocky habitat. It is a perennial herb forming a small clump or mat of very slender, tangling red stems. The stems are lined with pairs of slightly woolly oval-shaped leaves 2 to 9 millimeters wide. The tiny inflorescence is a cyathium less than 2 millimeters wide. The cyathium is a bell-shaped array of white, scalloped petal-like appendages surrounding the actual flowers. Each appendage has at its base a shiny red nectar gland. At the center of the appendages is a ring of male staminate flowers around a single female flower. The female flower develops into an oval-shaped fruit which bears wrinkled white seeds.