The solitary duckbill eel (Nettastoma solitarium) is an eel in the family Nettastomatidae (duckbill/witch eels). It was described by Castle and Smith in 1981. It is a marine, deep water-dwelling eel which is known from the Indo-Western Pacific, including Kyushu-Palau Ridge, the Philippines, Australia, and the Hawaiian Islands. It is known to dwell at a depth range of 415 to 610 metres (1,362 to 2,001 ft). Males can reach a maximum total length of 46.5 centimetres (18.3 in).