There are several instances of the species Tyrannosarus Rex in the Fossil Fighters franchise.
- For the vivosaur in Fossil Fighters and Fossil Fighters: Champions known as T-Rex, see T-Rex (DS).
- For the tyrannosaurid boneysaur used by Cole and Lester in Champions, see B-Rex (DS).
- For the tyrannosaurid zombiersaur used by Zongazonga in Champions, see Z-Rex (DS).
- Fossil Fighters: Frontier has a trio of T-Rex.
- T-Rex Sue shares design elements with Rex (DS), and is a Fire vivosaur.
- T-Rex Stan is a different take on the Tyrant King; being Air element it has an elemental advantage against Earth vivosaurs that almost all previous incarnations had (excepting Z-Rex), but conversely it's the first in its family to be weak to Fire.
- Tyrannosaurus is playable in the game, available as "special content" via AR Cards.