Agaricus californicus, commonly known as the California Agaricus, is a poisonous mushroom in the section Xanthodermati of the genus Agaricus. It is mildly poisonous, causing gastrointestinal upset in many individuals. The etiology of these symptoms is unclear and some individuals can eat it without experiencing symptoms, but since there is no way to tell who can eat the mushroom safely it is generally recommended against.