Rivoli's hummingbird (Eugenes fulgens) is a large hummingbird. It was usually considered the only member of the genus Eugenes and is also called the magnificent hummingbird. Many taxonomic authorities, such as the International Ornithological Committee, split the northern nominate subspecies E. f. fulgens from the larger southern race of Costa Rica and Panama, E. f. spectabilis, into distinct species in which case the nominate fulgens is renamed Rivoli's hummingbird and spectabilis is named the Talamanca hummingbird or admirable hummingbird.
Rivoli's hummingbird species ranges from 11–14 cm (4.3–5.5 in) in length and weighs from 6 to 10 g (0.21 to 0.35 oz), with males typically a little larger than females. The bird has a wingspan of 18 centimetres (7.1 in). Of the hummingbirds found in the United States, Rivoli's hummingbird is one of the two largest species, rivaled in size only by the blue-throated hummingbird. The black bill is long and straight to slightly curved. Both sexes look very dark unless the sun catches the iridescence of the plumage and the brilliant colours flash in the sunlight.