Cornish people ( Cornish : Kernowyon ) are often regarded as a distinct ethnic group or national identity of the United Kingdom , originating in Cornwall . For some , the Cornish represent a distinct ethnic group within the UK , which can trace its roots to the ancient Britons who inhabited southern and central Great Britain prior to the Roman conquest , and many in the county today continue to assert a distinct identity , separately or in addition to English or British identities . Cornish identity has been adopted by migrants into Cornwall , as well as by emigrant and descendant communities from Cornwall , the latter sometimes referred to as the Cornish diaspora .