Ophioglossum californicum, known by the common name California adder's tongue, is an uncommon species of fern in the family Ophioglossaceae. The fern is native to California, and Baja California in Northwestern Mexico. It is found in the San Joaquin Valley, Sierra Nevada foothills, and along the central and southern coast regions. Habitats include moist areas, such as wet pastures and vernal pools, coastal grasslands, and coastal/montane/interior chaparral micro-habitats. It becomes very rare in dry years.