G21

G21 may refer to:


 * BMW 3 Series (G21), an automobile
 * County Route G21 (California)
 * Glock 21, a firearm
 * Gribovsky G-21, a Soviet aircraft
 * Grumman G-21 Goose, an American aircraft
 * Ginetta G21, an automobile produced by Ginetta Cars
 * G21 developing nations, a trade bloc also known as G20 developing nations