Psychotria kosraensis Lorence & K. R. Wood (Rubiaceae, Rubioideae), a narrow endemic from Kosrae, Caroline Islands, Federated States of Micronesia (FSM), is described and illustrated. The new species differs from other known species of Psychotria L. in Micronesia by its combination of narrowly obovate-elliptic or narrowly elliptic leaves with long-acuminate apex and abaxially barbate leaf axils, pseudoaxillary fasciculate inflorescences with very short peduncles ca. 1 mm, flowers with a long calyx tube with narrowly triangular lobes, and villosulous fruits crowned with the persistent well-developed calyx tube and lobes. Known from a single population of five individuals, P. kosraensis easily falls into the IUCN Red List category of Critically Endangered (CR).