| Named By: | Richard Owen in 1859 |
| Time Period: | Induan-Olenekian, 252.17-247.2 Ma |
| Location: | South Africa - Normandien Formation (Harrismith Member), Lystrosaurus other zone |
| Size: | Largest skull roughly up to 12 centimetres long. Larger remains indicate a total adult length of about 75-80 centimetres long |
| Diet: | Carnivore |
| Fossil(s): | Skull and post cranial remains of individuals of various ages |
| Classification: | | Chordata | Synapsida | Cynodontia | Galesauridae | |
| Also known as: | | Glochinodontoides gracilis | |
Galesaurus (from the Greek roots for 'weasel' and 'lizard') was a prehistoric carnivorous therapsid that lived between the Induan and the Olenekian age in what is now South Africa. It was incorrectly classified as a dinosaur by Sir Richard Owen in 1859.
Notably, Galesaurus was mentioned in the first issue of Nature in 1869, where T. H. Huxley expressed confidence that it would eventually be shown to be a dinosaur. However, current opinion is that it was not a dinosaur and belongs to a mammal-like group called Cynodonts.