A new species of synaphobranchid eel, Dysomma opisthoproctus, is described on the basis of a single specimen from the northeastern coast of Taiwan at depth about 200 m. It is characterized by a posteriorly positioned anus (1.5 times head length behind pectoral-fin base), well-developed cheek papillae, seven or eight compound dentary teeth, four compound vomerine teeth, four infraorbital pores, three supraorbital pores, seven preoperculomandibular pores, and 120 vertebrae (35 preanal vertebrae).