Gamay is a purple-colored grape variety used to make red wines, most famously grown in Beaujolais. Its full name is Gamay Noir à Jus Blanc, and it is probably originated as a mutation of Pinot Noir.
Confusingly the Gamay name has become attached to other varieties grown in California which were at one time were thought to be the true Gamay. Napa Gamay is now known to be Valdeguié and the name Napa Gamay will no longer appear on labels after 2007. Gamay Beaujolais is considered to be an early ripening Californian clone of Pinot Noir.
Gamay Noir is a permitted synonym for Gamay in the US.