The Red Bull is an evil magical creature and the secondary antagonist from the 1982 animated fantasy film The Last Unicorn, and the classic 1968 fantasy novel of the same name by Peter S. Beagle. He appears in the form of a bull covered in fire and is used by the evil King Haggard to herd Unicorns into the sea to keep him happy. He figures in many contradictory legends in the world of The Last Unicorn, which leave his true nature in doubt. Whether the Bull is a living monster or a spirit is uncertain, as is how Haggard found him.
He was voiced by Frank Welker.
Molly, Schmendrick, and the Unicorn leave Hagsgate and continue toward Haggard's castle, but on their way they are attacked by the Red Bull. The Unicorn runs, but is unable to escape the bull. The Bull chases her, not attacking, but breaking her spirit, until she almost allows him to herd her to the sea. In an effort to aid her, Schmendrick unwittingly turns the Unicorn into a human female. Confused by the change, the Red Bull gives up the pursuit and disappears.
Later on Molly, Schmendrick, the Unicorn (now called Lady Amalthea) and Prince Lir discover the lair of the Red Bull. The Bull eventually becomes no longer fooled by the Unicorn's human form and starts to attack. Schmendrick changes the Unicorn back, and the Red Bull gives chase to her once more. The Unicorn and the Bull keep on chasing each other on the beach, but Prince Lir, determined to save the Unicorn, steps in front of the Red Bull, and is killed. Enraged at Lir's death, the Unicorn gathers her courage and starts attacking and herding the Red Bull towards the sea. The Red Bull then disappears into the sea, defeated. His master himself would meet this fate shortly afterwards, as the imprisoned unicorns break free from the sea and destroy King Haggard's castle, which causes Haggard to fall to his death, joining the Bull in the sea.
The Red Bull is a dangerous, powerful, violent, and demonic beast who attacks persistently. He pursues whatever target his master sets him against relentlessly. He is blind, and is only aware of his target. Anything or anyone that gets in its way is destroyed with hardly any awareness from the Bull (as shown when Prince Lir tried to stop it). Even an immortal creature, like a Unicorn, becomes filled with blind terror at the sight of it. Despite his savage and obstreperous nature, he is also very loyal and affectionate to his master, King Haggard, who used it to herd the unicorns to the sea near his castle.
Though Haggard commands the Bull, he does not own it. He explains in the novel that the Bull is simply an entity that serves anyone who has no fear for as long as that person lives, hinting that the Red Bull is probably a personification of fear - he inspires horror in anything he pursues, but once he is confronted by his victim, as the Unicorn confronts him in the end, he is powerless to fight back.
- Even though King Haggard was the true main antagonist of the film, the Red Bull served as The Heavy because it was his quest to rustle the unicorn race that drove the plot, which makes Haggard the Big Bad, and the one behind the plot.