The Deepwater big-eyed worm eel (Scolecenchelys castlei) is an eel in the family Ophichthidae (worm/snake eels). It was described by John E. McCosker in 2006. It is a subtropical, marine eel which is known from New Zealand, in the southwestern Pacific Ocean. It dwells at a depth range of 425-820 metres. Females can reach a maximum total length of 58 centimetres. The species epithet "castlei" was given in honour of Peter Henry John Castle.