The Sailfin eel (Paraletharchus pacificus, also known commonly as the Pacific sailfin eel in Mexico) is an eel in the family Ophichthidae (worm/snake eels). It was described by Raymond Carroll Osburn and John Treadwell Nichols in 1916, originally under the genus Letharchus. It is a marine, tropical eel which is known from the eastern central Pacific Ocean (from which its species epithet is derived), including Costa Rica, Mexico, and Panama. It is known to dwell at a depth of , and inhabits rock and sand sediments. Males can reach a maximum total length of .
Due to its wide distribution, lack of known threats, and lack of observed population decline, the IUCN redlist currently lists the Sailfin eel as Least Concern.