C. nigra

C. nigra may refer to:

Animals

 * Cardiocondyla nigra, an ant species in the genus Cardiocondyla
 * Ciconia nigra, a large wading bird species
 * Coracopsis nigra, a black coloured parrot species native to Comoros, Madagascar, Mayotte and Seychelles
 * Chelonoidis niger, the largest living species of tortoise, often historically misspelled as "nigra"

Plants

 * Carex nigra, a perennial plant species native to wetlands of Europe and Siberia
 * Crataegus nigra, a hawthorn species
 * Centaurea nigra, a flowering plant species