Macrognathus is a genus of eel-like fish of the family Mastacembelidae of the order Synbranchiformes.

[1] Macrognathus species feed on small aquatic insect larvae as well as oligochaetes.

However, they differ in a more modified rostrum, which may be slightly to significantly larger and longer than those found in Mastacembelus.

[1] A number of species of this genus are popular aquarium fish.

[2] According to Catalog of Fishes, one of these, M. malabaricus, belongs in the genus Mastacembelus instead of Macrognathus and another, M. taeniagaster, is considered a junior synonym of M.