Gy

Gy or GY may refer to:

In Measurement:
* gray (unit) (Gy), SI unit of absorbed radiation
* giga-year (see Byr), 1,000,000,000 years (non-SI)
* A galactic year, the time it takes for the solar system to orbit the galactic center

Places:
* Gy, Switzerland, a village in the Geneva canton
* Guyana (ISO country code: GY)
* GY postcode area for Guernsey
* 'GY' is a term for Grimsby, United Kingdom in its local dialect
* Gy, a commune in the Haute-Saône département of France

In transport:
* GY, a Mazda automotive piston engine
* Gabon Airlines (IATA code: GY)
* GY, IATA code for Tri-MG Intra Asia Airlines and Guyana Airways 2000

People:
*Pierre Gy, French chemist and statistician
*Garin de Gy, 14th century Catholic Master of the Order of Preachers

Other:
* Hungarian gy, an alphabetic digraph
* a digraph in the Tibetan Pinyin transliteration system
* GenCorp Inc. (GY NYSE symbol)
* Green Youth (disambiguation), one of two Green party youth wings