A 15-kilo fish with a flat body, short tail, and round head was caught by a fisherman off the central province of Nghe An.
Ho Van Doan, who caught the fish, said it died one hour after being brought ashore.
Some elders in Quynh Luu commune where Doan lives have claimed that the fish is classified as a sunfish, or a Mola Mola, that rarely appears in the country’s waters.
The frozen fish will be handed over to the Vietnam National Museum of Nature for preservation.
The Mola Mola is native to tropical and temperate waters around the globe. In Vietnam, the fish is listed in the Red Book of species in need of strict protection.