| Named By: | P. D. Gingerich, M. Arif & W. C. Clyde in 1995 |
| Time Period: | Middle Eocene |
| Location: | Pakistan - Domanda Formation |
| Size: | Uncertain |
| Diet: | Carnivore |
| Fossil(s): | Partial skull and post cranial skeletal remains including vertebrae and ribs |
| Classification: | | Chordata | Mammalia | Cetacea | Archaeoceti | Protocetidae | |
Gaviacetus (from Latin Gavia, "loon" and cetus, "whale") is an extinct archaeocete whale that lived approximately 45 million years ago. Gaviacetus was named for its characteristic narrow rostrum and the fast pursuit predation suggested by its unfused sacral vertebrae.