Mastacembelus pentophthalmos Gronow, 1854 Macrognathus pentophthalmos, the Sri Lanka five-eyed spiny eel, is a small species of spiny eel that is endemic to freshwater habitats in Sri Lanka.

[5] Compared to Mastacembelus armatus, the only other spiny eel in Sri Lanka, M. pentophthalmos has a striped/plain (not mottled) pattern, and clearly separated dorsal, caudal and anal fins.

[3] The English name of M. pentophthalmos refers to the series of dark spots on its dorsal fin.

[3] Described as a new species in 1854, it was then considered a synonym of the widespread M. aral.

In 2008 it was shown that this was mistaken and M. pentophthalmos was reinstated as a valid species (the true M. aral is not found in Sri Lanka).