The Rite of Spring is the fourth and longest segment in Fantasia. It mainly focuses on the Big Bang and the Dinosaur age.
The whole score starts off with outer space at the start of the bassoon solo that it goes back in time, back to the fantastic, to 4.5 billion years ago. We see the Milky Way Galaxy coming out of the darkness. Comets, the sun, and shooting stars whiz by. We come down to a planet which is Earth being born and pass by the Earth's moon down to the surface. Light from the volcanoes light up and the volcanoes burst with lava. Then the volcanoes explode. Lava pours down from a volcano with rocks and hits the water, creating a storm and the sea to rise up, flooding the volcano and everything around. Then everything went silent.
The scene changes to the sea when we see the cells like the Choanoflagellates, and blue microscopic blobs that split up, until the black smoke came. We see many sea creatures as the ages rolled by. One of the fish went up to land and became the first amphibian to crawl on land. Later, the dinosaurs appear, living their lives of what dinosaurs do. Up on top of a cliff, Pteranodons swoop down to catch fish. One of them caught a fish but is pulled down by a Tylosaurus.
Everything was going so quiet for the dinosaurs. Every dinosaur is doing what the dinosaurs would do. Until then, they look up ahead, as rain begins to fall, and see the Tyrannosaurus rex. It chases the dinosaurs and bites the Stegosaurus' tail. The Stegosaurus and the T-rex both fight, with the T-rex biting the Stegosaurus' neck and the Stegosaurus using its tail to beat the T-rex. The dinosaurs look on while Stegosaurus does its last two hits and T-rex bites its neck and brings it down, killing it. The dinosaurs leave while T-rex eats its remains.
Later, everything was destroyed. There was no food and water for the dinosaurs, nothing but dried up pools, branches, ruined trees, and mud. The sun is too hot for them. The dinosaurs move on and some of them are stuck in the mud with Ceratosaurus coming to them. The wind blows and some dinosaurs collapse, including the T-rex. Later, footprints are seen and we see the bones of the dinosaurs, showing that they are now extinct 65 million years ago.
Just as the moon began to form an eclipse with the sun, an earthquake suddenly erupted, wiping the dinosaur bones away. The wind then blew a storm and the sea inland, the lowland and everything around became completely flooded, and everything was silent once again. In the end, when the eclipse was complete, you see it set over the world of sea and land. The film then goes to the intermission, which has the only appearance of the Fantasia title card (which was omitted on the 1991 UK VHS release).
List of cells that appeared
List of animals that appeared
- A narrated version of the segment, titled "A World is Born", was produced as a school educational filmstrip in 1955, narrated by Holling C. Holling. It was a mainstay in science classes of the 50s and 60s and would inspire paleontologists such as Stephen Jay Gould to pursue it as a profession.
- The eclipse was used in the 1980 horror film The Watcher in the Woods.
- The scene where the dinosaurs turn around to see the Tyrannosaurus rex is reused in Mickey's House of Villains where the villains turn to see Mickey ready to battle Jafar.
- This segment was originally going much longer and would have shown the age of mammals as well as the dawn of man ending with humans creating fire and dancing triumphantly around a fire circle, but this was sadly scrapped due to human evolution being a controversial subject matter during the 1940s. 
- However, a few pieces of concept have surfaced online in the past few years. One piece of artwork uploaded to the internet, which was done in 2006, done by the late artist Kay Nielsen shows a pair of saber-toothed cats (Smilodon fatalis) stalking a trio of woolly mammoths (Mammuthus primigenius).
- Igor Stravinsky, the composer of The Rite of Spring, would ultimately dislike Fantasia as a result of the score being re-edited without his permission, alterations that were the result of the aforementioned Age of Mammals and Early Man scenes being cut.
- Musical Score: Igor Stravinsky – Le Sacre du printemps
- Directed by Bill Roberts and Paul Satterfield
- Story Development/Research: William Martin, Leo Thiele, Robert Sterner, and John Fraser McLeish
- Art Direction: McLaren Stewart, Dick Kelsey, and John Hubley
- Background Paintings: Ed Starr, Brice Mack, and Edward Levitt
- Animation Supervision: Wolfgang Reitherman and Joshua Meador
- Animation: Philip Duncan, John McManus, Paul Busch, Art Palmer, Don Tobin, Edwin Aardal, and Paul B. Kossoff
- Special Camera Effects: Gail Papineau and Leonard Pickley