The Cornish language revival is an ongoing process to revive the use of the Cornish language of Cornwall, England. The Cornish language's disappearance began to hasten during the 13th century, but its decline began with the spread of Anglo-Saxon in the 4th and 5th centuries. The last reported person to have full knowledge of a traditional form of Cornish, John Davey, died in 1891. The revival movement started in the late 19th century as a result of antiquarian and academic interest in the language, which was already extinct, and also as a result of the Celtic revival movement. In 2009, UNESCO changed its classification of Cornish from "extinct" to "critically endangered", seen as a milestone for the revival of the language.

Cornish is a Southwestern Brittonic language of the Celtic language family. Along with Welsh and Breton, Cornish is descended from the Common Brittonic language spoken throughout much of Great Britain before the English language came to dominate. For centuries, until it was pushed westwards by English, it was the main language of Cornwall, maintaining close links with its sister language Breton, with which it was mutually intelligible, perhaps even as long as Cornish continued to be spoken as a vernacular. Cornish continued to function as a common community language in parts of Cornwall until the mid 18th century, and there is some evidence for traditional speakers of the language persisting into the 19th century.