Gwangi is the titular main antagonist of the 1969 fantasy-western film The Valley of Gwangi.
His vocal sound effects were provided by Selwyn Petterson.
Gwangi is a large carnivorous theropod dinosaur that tyrannizes prehistoric life forms that live in the Forbidden Valley (a place lost in the mountains of Mexico where time has stood still in prehistoric times), of which it is undisputedly dominant for strength and ferocity, to the point of being feared by the Gypsies who live near the valley and be believed by them as a supernatural and evil entity. It is high around 19 ft, has a skin of a bright blue shocking color, an upright posture (since the film was shot in 1968, the animal's appearance is based on the erroneous depictions of the dinosaurs in vogue in the first decades of the Twentieth Century), strong front legs armed with three claws each that allow him a grip on the prey and razor-sharp teeth. Although at the time the film was shot, it was a common opinion that dinosaurs were slow-moving animals, Gwangi is capable of very agile movements, and is very strong in combat.
Temperamentally, Gwangi is extremely aggressive, and even endowed with a semblance of cruelty and sadism: he assails any form of life in front of him with fury and extreme ferocity, and sometimes kills his prey without even eating it (much like the Indominus rex of Jurassic World).
For many years Gwangi has established himself as a dominant predator in the Forbidden Valley, until, at the end of the Nineteenth Century, the owner of a local rodeo discovers a tiny horse coming from the Valley, realizing that it is a prehistoric species of horses called Eohippus. However, a group of superstitious gypsies believe that the small animal must be returned to the Forbidden Valley and, after having kidnapped it, it goes towards the canyon behind which the valley hides. Followed by a group of rodeo cowboys, the two groups enter the Valley where they run into Gwangi, who tries to kill and eat the group. After witnessing the fierce fight between Gwangi and a Styracosaurus (won by the carnivore, which kills the herbivore) and losing one of their mates, the cowboys try - unsuccessfully to capture Gwangi with their lassos, after which they try to escape through a narrow fissure. Gwangi, however, follows them, causing a landslide that hits him leaving him momentarily stunned. The cowboys can then capture the creature and transport it to the city, so as to show it in the rode arena.
On the day of the show, one of the Gypsies, continuing to believe that everything from the Forbidden Valley is cursed and should not be allowed among the opening men, tries to free Gwangi but the dinosaur gets free and embarks on a rampage through the city, fighting furiously and killing one of the circus elephants in the process. Many of the city's inhabitants sought refuge in the local cathedral, but Gwangi splits his way into the building in search of prey. Inaugurating the citizens outside the back door, one of the cowboys manages to set the church on fire, burning the beast alive and ending its threat.
- Gwangi was created by the late Ray Harryhausen, the legendary stop-motion special effects curator who created other famous monsters like the Krakon from Clash of the Titans or the Rhedosaurus from The Beast from 20,000 Fathoms. The inspirational model of Harryhausen was the Tyrannosaurus rex from the 1925 film The Lost World, which was worked by the late Willis O'Brien (who was Harryhausen's mentor).
- Officially, Gwangi is called an Allosaurus, but its appearance is different from that of the aforementioned animal, resembling much more to the aforementioned Tyrannosaurus rex of the 1960 film The Lost World or to that of the 1933 film King Kong by the late Merian C. Cooper and the late Ernest B. Schoedsack. In the 2003 book Ray Harryhausen: An Animated Life, Harryhausen refers to Gwangi as a Tyrannosaurus rex, or as a hybrid species between T. rex and Allosaurus called "Tyrannosaurus Al".
- Like most early era dinosaur films the Gwangi bears little resemblance to how actual dinosaurs functioned in the real world, this is more apparent in other dinosaur movies of the era which had Triceratops and other herbivorous dinosaurs as man-eaters: treating them more as large monsters than animals (due to the fact that dinosaurs were not very well researched in that time period).