Limia islai, new species of livebearing fish, is described from Lake Miragoane in southwestern Haiti on Hispaniola. The new species herein described has a conspicuous barred pattern consistent in several (4 to 12) black bars along the body, ray 4p serrae of the gonopodium in males with 10 segments and origin of dorsal fin in females slightly behind of origin of anal fin. Although the new species color pattern is similar to the Humpbacked Limia Limia nigrofasciata Regan 1913, L. islai sp. nov. has exclusive morphological features, such as slender body, lack of hump anterior to dorsal fin in males and presence of specific features in the gonopodial suspensory, which allow an unambiguous diagnosis from L. nigrofasciata. Limia islai further differs from L. nigrofasciata in reproductive behavior since L. islai males rely on sneak copulations and gonopodial thrusting, whereas L. nigrofasciata display an elaborate courtship behavior. The new species is also genetically distinct in both nuclear (Rh, Myh6) and mitochondrial (12S, ND2, D-loop, Cytb) genes from other species in the genus showing reciprocal monophyly. The description of this new Limia species from Lake Miragoane confirms this lake as an important center of endemism for the genus with a total of eight endemic species described so far. This article is protected by copyright. All rights reserved.