Rhamnus alnifolia is a species of flowering plant in the buckthorn family known by the common names alderleaf buckthorn, or alder buckthorn. It is native to North America, where it is known mainly from the southern half of Canada and the northern half of the United States and California. It can be found in forested habitat. Rhamnus alnifolia is a spreading shrub approaching two meters in maximum height, its thin branches bearing deciduous leaves. The thin, deeply veined leaves have oval blades up to 10 centimeters long, pointed at the tip and lightly toothed along the edges. The inflorescence is a solitary flower or umbel of up to three flowers occurring in leaf axils. The tiny flowers are just a few millimeters wide and lack petals. Female flowers drupes just under a centimeter wide, each containing three seeds. The drupes darken to black when ripe. Rhamnus alnifolia is a spreading shrub approaching two meters in maximum height, its thin branches bearing deciduous leaves. The thin, deeply veined leaves have oval blades up to 10 centimeters long, pointed at the tip and lightly toothed along the edges. The inflorescence is a solitary flower or umbel of up to three flowers occurring in leaf axils. The tiny flowers are just a few millimeters wide and lack petals. Female flowers drupes just under a centimeter wide, each containing three seeds. The drupes darken to black when ripe.