| Named By: | Joseph Leidy in 1856 |
| Time Period: | Late Cretaceous, 77.5-76.5 Ma |
| Location: | North America |
| Size: | 2.4 meters long |
| Diet: | unavailable |
| Fossil(s): | Many individuals recovered |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Theropoda | Troodontidae | Troodontinae | |
| Also known as: | | Pectinodon bakkeri | Polyodontosaurus grandis | Stenonychosaurus inequalis | |
Troodon ( TROH-a-don; Troodon in older sources) is a dubious genus of relatively small, bird-like dinosaurs known definitively from the Campanian age of the Cretaceous period (about 77 mya). It includes at least one species, Troodon formosus, is known from Alberta and Montana. Discovered in 1855, T. formosus was among the first dinosaurs found in North America, although it was thought to be a lizard until 1877.
The genus name is Greek for "wounding tooth", referring to the teeth, which were different from those of most other theropods known at the time of their discovery. The teeth bear prominent, apically oriented serrations. These "wounding" serrations, however, are morphometrically more similar to those of herbivorous reptiles, and suggest a possibly omnivorous diet.