Cornish Americans (Cornish: Amerikanyon gernewek) are Americans who describe themselves as having Cornish ancestry, an ethnic group of Brittonic Celts native to Cornwall and the Scilly Isles, part of the United Kingdom. Although Cornish ancestry is not recognized on the United States Census, Bernard Deacon at the Institute of Cornish Studies estimates there are close to two million people of Cornish descent in the U.S., compared to half a million in Cornwall itself and only half of those Cornish by descent.

Tangier Island is an island in lower Chesapeake Bay in Virginia: some inhabitants have a West Country accent that traces back to the settlers (including the Cornish) who arrived there in the 1600s.

The coincidence of the decline of the mining industry in Cornwall in the 19th century and the discovery of large amounts of mineral deposits abroad meant that Cornish families headed overseas for work. Each decade between 1861 and 1901, a fifth of the entire Cornish male population migrated abroad – three times the average for England and Wales. In total, the county lost over a quarter of a million people between 1841 and 1901.

Large numbers of Cornish people moved to the United States, and while some stayed in New York City and other East Coast ports after arriving, many moved inland to mining areas in California, Wisconsin, Pennsylvania and Michigan (the Upper Peninsula.) One such area was Mineral Point, Wisconsin, in which the largest group of immigrants were Cornish miners attracted to the lead mining opportunities, and by 1845 roughly half of the town's population had Cornish ancestry. Today the Cornish town of Redruth is twinned with Mineral Point.

Mineral Point, Wisconsin serves Cornish food, such as pasties and figgyhobbin, and Cornish pasties are sold at ex-Cornish mining towns in America, especially in Butte, Montana and the Upper Peninsula of Michigan.

In California, statues and monuments in many towns pay tribute to the influence of the Cornish on their development. In the city of Grass Valley, the tradition of singing Cornish carols lives on and one local historian of the area says the songs have become "the identity of the town". Some of the members of today's Cornish Carol Choir are in fact descendants of the original Cornish gold miners. The city holds St Piran's Day celebrations every year, which along with carol singing, includes a flag raising ceremony, games involving the Cornish pasty, and Cornish wrestling competitions. The city is twinned with Bodmin in Cornwall.

Cornish culture continues to have an influence in the Copper Country of northern Michigan, the Iron Ranges of northern Michigan, Wisconsin and Minnesota, and Butte, Montana.

There were many famous Cornish wrestling champions from the U.S. including many world champions.