The polychelids are large, uncommon, primitive decapods that inhabit the depths of the world oceans down to 5000 m, between latitudes 50°N and 55°S. A study of major deep-sea collecdons led to a revision of the family. All genera and species are redescribed and extended synonymies given. Two new genera are established: Cardus, for Polycheles crucifer (Thomson, 1873) and Homeryon, for Polycheles asper Rathbun, 1906 and a new species, H. armarium. The genus Pentacheles Bate, 1878, is revived to include polychelids in which the epipod on third maxilliped is longer than the ischium: P. gibbus Alcock, 1894, P. laevis Bate, 1878, P. obscurus Bate, 1878, P. synderi (Rathbun, 1906) and P. validus A. Milne Edwards, 1880. Stereomastis Bate, 1888 is considered a synonym of Polycheles Heller, 1862. Willemoesia Grote, 1873 is retained with but four species: W. forceps A. Milne Edwards, 1880, W. inornata Faxon, 1893, W. leptodactyla (Willemoes-Suhm, 1875), and W. pacifica Sund, 1920. In all, thirty-two species are recognized, including six new species. The bathymétrie and geographic ranges are amended and discussed. A key to the genera and species of the family is provided.