The Valley of Gwangi is a 1969 American fantasy Western film produced by Charles H. Schneer and Ray Harryhausen, directed by Jim O'Connolly, written by William Bast, and starring James Franciscus, Richard Carlson, and Gila Golan.
Creature stop-motion effects were by Harryhausen, the last dinosaur-themed film that he animated. He had inherited the film project from his mentor Willis O'Brien, responsible for the effects in the original King Kong (1933). O'Brien had planned to make The Valley of Gwangi decades earlier but died in 1962 before it could be realized. Producer Charles Scheer called it "probably the least of the movies Ray and I made together."
In Mexico at the turn of the 20th century, a cowgirl named T.J. Breckenridge hosts a struggling rodeo. Her former lover, Tuck Kirby, a heroic former stuntman working for Buffalo Bill's Wild West Show, wants to buy her out. Along the way, he is followed by a Mexican boy named Lope, who intends to join the rodeo on a quest for fame and fortune. T.J. is not interested in Tuck because of this, but Tuck is still attracted to T.J., especially when T.J. jumps off a diving board on her horse. T.J. finally accepts Tuck when he saves Lope from a bull and Tuck and T.J. kiss.
T.J. has an ace she hopes will boost attendance at her show – a tiny horse called El Diablo. Tuck meets a British paleontologist named Horace Bromley, who is working in a nearby Mexican desert. Bromley shows Tuck fossilized horse tracks, and Tuck notes their similarity to El Diablo's feet. Tuck sneaks Bromley into the circus for a look at El Diablo, and Bromley declares the horse to be a prehistoric Eohippus.
The tiny horse came from a place known as the Forbidden Valley. A gypsy known as Tia Zorina claims that the horse is cursed, and demands that it be immediately returned. Later, she and the other gypsies collaborate with Bromley to steal El Diablo and release it back in the valley. Bromley hopes to follow the horse to its home in search of other prehistoric specimens. Carlos, an ex-member of the Gypsy tribe now working for T.