Alpheus cedricisp. n. is described based on two specimens collected under rocks while scuba diving off the coast of Ascension Island, central Atlantic Ocean. The new species belongs to the Alpheus macrocheles (Hailstone, 1835) species complex and appears to be most closely related to the eastern-central Atlantic Alpheus macrocheles, the western Atlantic Alpheus amblyonyx Chace, 1972, and the eastern Pacific Alpheus bellimanus Lockington, 1877 and Alpheus rectus Kim & Abele, 1988. However, it differs from all these species by a combination of morphological characters and by a diagnostic and striking colour pattern.
Keywords: Alpheidae; Alpheus; Ascension Island; Atlantic Ocean; Caridea; new species.