Syphacia (Syphacia) rifaii sp. n. (Nematoda: Oxyuridae) is described from endemic Bunomys chrysocomus and Bunomys prolatus (Rodentia: Muridae) on Sulawesi Island, Indonesia. The new species is closest morphologically to Syphacia (Syphacia) sulawesiensis, parasitic in Rattus xanthurus from Sulawesi Island, by having large vesicular lateral alae in males, but is readily distinguished by having a smaller body, a round cephalic plate in both sexes, the absence of lateral alae in females, a longer relative distance between excretory pore and vulva, and smaller eggs. Syphacia (S.) rifaii is surmised to be a specific parasite of Bunomys spp. and has evolved from a common ancestor with S. (S.) sulawesiensis on Sulawesi Island.