| Named By: | Alberto Luis Cione, Wasila M, Dahdul, John G. Lundberg & Antonio MachadoinAllison in 2009 |
| Time Period: | Late Miocene |
| Location: | Argentina |
| Size: | Estimated up to 1 meter long |
| Diet: | Uncertain, probably carnivorous, but teeth could have been used for a herbivorous diet |
| Fossil(s): | Premaxillae teeth |
| Classification: | | Chordata | Actinopterygii | Characiformes | Characidae | Serrasalminae | |
Megapiranha paranensis or megapiranha is an extinct serrasalmid characin fish from the Late Miocene (8-10 million years ago) of Argentina, described in 2009. It is thought to have been about 71-128 centimetres (2.33-4.20 ft) in length. The holotype consists only of premaxillae and a zigzag tooth row; the rest of its body is unknown. This dentition is reminiscent of both the double-row seen in pacus, and the single row seen in the teeth of modern piranhas, suggesting that M. paranensis is a transitional form. Its bite force is estimated between 1,240-4,749 N (279-1,068 lbf).