The Xerces Society for Invertebrate Conservation is a non-profit environmental organization that focuses on the conservation of invertebrates considered to be essential to biological diversity and ecosystem health. It is named in honor of an extinct California butterfly, the Xerces blue.

The Xerces blue is a recently extinct species of butterfly in the gossamer-winged butterfly family, Lycaenidae. The species lived in coastal sand dunes of the Sunset District of the San Francisco Peninsula in California. The Xerces blue is believed to be the first American butterfly species to become extinct as a result of loss of habitat caused by urban development. The last Xerces blue was seen in 1941 or 1943 on land that is now part of the Golden Gate National Recreation Area.