The International Olympic Committee (IOC) uses three-letter abbreviation country codes to refer to each group of athletes that participate in the Olympic Games. Each geocode usually identifies a National Olympic Committee (NOC), but there are several codes that have been used for other instances in past Games, such as teams composed of athletes from multiple nations, or groups of athletes not formally representing any nation.
Several of the IOC codes are different from the standard ISO 3166-1 alpha-3 codes. Other sporting organisations like FIFA use similar country codes to refer to their respective teams, but with some differences. Still others, such as the Commonwealth Games Federation or Association of Tennis Professionals, use the IOC list verbatim.