| Named By: | Joseph Leidy in 1869 |
| Time Period: | Late Oligocene to Early Miocene |
| Location: | USA, Nebraska, Oregon, South Dakota and Wyoming |
| Size: | About 25 - 30 centimetres long |
| Diet: | Herbivore |
| Fossil(s): | Multiple individuals |
| Classification: | | Chordata | Mammalia | Rodentia | Castoridae | Palaeocastorinae | |
| Also known as: | | Capacikala sciuroides | Steneofiber nebrascensis | Steneofiber peninsulatus | Steneofiber sciuroides | |
Palaeocastor ('prehistoric beaver') is an extinct genus of beavers that lived in the North American Badlands during the late Oligocene period.