Gwangi is the title character and main antagonist in the 1969 classic, The Valley of Gwangi. He is described as a male Allosaurus.
Sometime near the turn of the 20th century, a beautiful cowgirl named T.J. Breckenridge (Gila Golan) hosts a rodeo that is struggling. Her former fiancé Tuck Kirby (James Franciscus), a heroic former stuntman working for Buffalo Bill's Wild West show, wants to buy out T.J.
T.J. has an ace she hopes will boost attendance at her show - a tiny horse. Tuck meets a British paleontologist named Horace Bromley (Laurence Naismith), who was working in a nearby Mexican desert. Bromley shows Tuck fossilized horse tracks, which Tuck notices to be similar to T.J.'s horse's feet. So Tuck sneaks Bromley in for a peek. Bromley declares the horse to be an Eohippus.
The tiny horse came from a place known as the Forbidden Valley. A Gypsy known as Tia Zorina claims that it has a curse, and demands that it must be returned. Later, a group of thieves (presumably under orders from the Gypsy) collaborate with Bromley to steal the horse and release it in the valley. Bromley collaborates in the hopes of following the horse to its home. But Carlos (Gustavo Rojo), once a member of the Gypsy tribe now working for T.J.'s circus (and the one who actually delivered the tiny horse to T.J.), walks in on the theft and tries to stop it, but is knocked out.
Tuck arrives just as the Gypsy posse leaves. He sees Carlos as he begins reviving, notices the horse is missing, and sets off after it and Bromley. When T.J. and her crew discover Carlos and that the horse is missing, Carlos claims Tuck has stolen it. T.J. then leads a group of cowboys after Tuck and Bromley to retrieve the horse.
Making their way into the Forbidden Valley, Tuck, T.J, and the rest of the group meet up and soon discover why the valley is said to be cursed as a Pteranodon swoops down and snatches a boy who had accompanied them. After Carlos kills the Pteranodon, they spot an Ornithomimus, a small dinosaur which they chase after in the hopes of capturing it. Just as the ornithomimus is about to escape, it is killed by Gwangi, a vicious Allosaurus which pursues the group, almost finding and eating Bromley. However, a Styracosaurus appears and drives Gwangi away.
Later, Gwangi pursues the people to their base camp, where it is able to get the best of them, until they begin to rope it down. Then, the Styracosaurus reappears and battles Gwangi. Gwangi emerges victorious, but decides to attack the men again.
Gwangi manages to catch and kill Carlos, but knocks itself out while trying to exit the valley in pursuit of the rest of the group. Securing the creature, they take it back to town where it is to be put on display in T.J.'s show. However, on opening night, one of the Gypsies sneaks in and begins to unlock Gwangi's cage in an effort to free it. Instead the unfortunate man is killed and Gwangi breaks free, killing Bromley and feasting on a circus elephant (actually modelled after a prehistoricmammoth) in the process. The crowd stampedes away from the arena, trampling and killing Tia Zorina.
Eventually, Gwangi, Tuck, T.J and Lope (a Mexican boy) end up in a cathedral which catches on fire. After some close calls, Tuck and T.J. manage to escape and lock the door behind them, trapping Gwangi in the burning building, which crumbles around it. Screaming in agony, Gwangi dies in the fire and the town makes Tuck the town hero. However, the townspeople are also saddened by the thought of a magnificent creature like Gwangi dying such a horrible death and by the loss of life caused by its rampage.
Gwangi was an extremely aggressive and hostile dinosaur, killing virtually anything he came across, and sometimes leaving his victims without eating them, in a similer fashion to the indominus rex from jurassic world. Despite the movie coming out before the dinosaur Renascence, gwangi was portrayed as very agile, and moved in a birdlike fashion. He also kept his tail off the ground most of the time. He was also fairly intelligent, knowing when his cage was unlocked. Despite being a bloodthirsty killer, he was still a basic animal, who seemed fearful when he was brought to the circus. And after rampaging through town, he managed to evoke sympathy as he screamed and wailed in agony as he was cooked alive in the cathedral.