These turtles, along with their cousin the Kemps ridley turtle, are best known for their unique mass nesting called Arribada, where thousands of females come together on the same beach to lay eggs.
The olive ridley was first described as Testudo mydas minor, Suckhow, 1798. It was later renamed Chelonian olivacea, Eschscholtz, 1829, and eventually Lepidochelys olivacea Fitzinger, 1843. Because Eschscholtz was the first to propose the specific epithet olivacea, though, he was credited with the valid name Lepidochelys olivacea Eschscholtz, 1829.
The genus name is derived from the Greek words lepidos, meaning scale, and chelys, which translates to turtle. This could possibly be a reference to the supernumerary costal scute counts characteristic of this genus. The etymology of the English vernacular name "olive" is somewhat easier to resolve, as its carapace is olive green in color. However, the origin of "ridley" is still somewhat unclear, perhaps derived from "riddle". Lepidochelys is the only genus of sea turtles containing more than one extant species: L. olivacea and the closely related L. kempii (Kemp's ridley).
Growing to about 2 feet in length, the Olive ridley gets its name from its olive-colored carapace, which is heart-shaped and rounded. Males and females grow to the same size; however, females have a slightly more rounded carapace as compared to the male. The heart-shaped carapace is characterized by four pairs of pore-bearing inframarginal scutes on the bridge, two pairs of prefrontals, and up to 9 lateral scutes per side. Olive ridleys are unique in that they can have variable and asymmetrical lateral scute 6 to 8 counts ranging from five to 9 plates on each side, with six to eight being most commonly observed. Each side of the carapace has 12–14 marginal scutes.
The carapace is flattened dorsally and highest anterior to the bridge. It has a medium-sized, broad head that appears triangular from above. The head's concave sides are most obvious on the upper part of the short snout. It has paddle-like forelimbs, each having two anterior claws. The upperparts are grayish green to olive in color, but sometimes appear reddish due to algae growing on the carapace. The bridge and hingeless plastron of an adult varies from greenish white in younger individuals to a creamy yellow in older specimens (maximum age is up to 50 years).