The enigma garden eel (Heteroconger enigmaticus) is an eel in the family Congridae (conger/garden eels). It was described by Peter Henry John Castle and John Ernest Randall in 1999. It is a marine, tropical eel which is known from the western Pacific Ocean, including Indonesia and Papua New Guinea. It dwells at a depth range of 3 to 25 m (9.8 to 82.0 ft), and inhabits regions with dark, silty sand and seagrass of the genus Holiphila. Males can reach a maximum total length of 43.7 cm (17.2 in), while females can reach 41.6 cm (16.4 in).