G. nigra

G. nigra may refer to:
 * Geochelone nigra, the largest living tortoise species, native to seven islands of the Galápagos archipelago
 * Gila nigra, the headwater chub, a fish species found in Arizona and New Mexico

Synonyms

 * Gymnadenia nigra, a synonym for Nigritella nigra, an orchid species found in Europe and Israel