Quercus peninsularis, common name peninsular oak, is a species of oak endemic to Baja California, Mexico. It is a shrub or small tree to 10 m, occurring in mountain valleys and canyons up to 3000 m. It is placed in section Lobatae. Leaves are 5âÂÂ8 cm, flat, leathery and hairy, with pointed tips and 2âÂÂ5 pairs of teeth. Flowers occur in 3 cm catkins. Fruits are 1.5 cm acorns, stemless, ovoid, with hairy cupules, maturing in a year. Mature bark is reddish; young twigs are thin and hairy.