The film includes the voices of Alan Arkin, Jeff Bridges, Mia Farrow, Angela Lansbury, and Christopher Lee. The musical score and the songs were composed and arranged by Jimmy Webb, and performed by the group America and the London Symphony Orchestra, with additional vocals provided by Lucy Mitchell. The film earned $2,250,000 on its opening weekend and grossed $6,455,330 domestically.
In an enchanted forest, a talking unicorn learns she is the very last of her kind. A butterfly reveals that a monstrous animal called the Red Bull herded her kind to the ends of the earth. Venturing into unfamiliar territory beyond the safety of her home, the Unicorn journeys to find them and bring them all back.
Upon her journey, the Unicorn is captured by the evil witch Mommy Fortuna and is put on display in Mommy Fortuna's Midnight Carnival. As most of the attractions are normal animals with a spell of illusion placed on them (to wit, a toothless lion for a Manticore, a paralyzed chimpanzee for a Satyr, and a mere snake for the Midgard Serpent), Fortuna uses a spell to create another horn on the unicorn's head that the non-magical carnival visitors can see, as they are unable to see her real form. Fortuna keeps the immortal harpy Celaeno captive as well and acknowledges the dangers of caging such a monster, but deems the risk secondary to the deed's recognition and prestige. While held captive, the unicorn is befriended by Schmendrick, an incompetent magician in the service of Mommy Fortuna. With the help of Schmendrick, the Unicorn escapes, in the process freeing Celaeno, who kills Fortuna and her henchman Ruhk. The Unicorn and Schmendrick later gain a second traveling companion Molly Grue, the careworn lover of Captain Cully (the disappointing "reality" behind the Robin Hood legend).
When the Unicorn nears the seaside castle of King Haggard, the keeper of the Red Bull, she encounters the animal, which turns out to be a monstrous fire elemental. At the last moment before her capture, Schmendrick uses his unpredictable magic and transforms her into a human woman with white knee-length hair. With her in this guise, the Red Bull is uninterested and departs. The Unicorn suffers tremendous shock at the feeling of mortality in her body. While Molly wraps the Unicorn's human form in a blanket, Schmendrick states that the magic, not he, chose the form, and promises that he will return her to normal after the quest is complete.
Schmendrick, Molly Grue, and the now-human Unicorn proceed to King Haggard's castle. Haggard is at first unwelcoming, and Schmendrick introduces the Unicorn as his niece Lady Amalthea. Schmendrick requests that the three of them stay there as members of Haggard's court, only to be told that the only occupants of the castle are Haggard, his adopted son Prince Lír and four ancient men-at-arms. Nonetheless, Haggard consents to lodge the trio, replacing his more competent on-call wizard, Mabruk, with Schmendrick, and setting Molly Grue to work in his scullery.
Amalthea begins to forget her identity and her reasons for coming to the castle and falls in love with Prince Lír as the result of the mortality of her current form. Caught in her newfound emotions, she struggles with thoughts of abandoning her quest for the sake of mortal love. Haggard confronts Amalthea in private conversation, hinting at the location of the unicorns, yet from the waning magic in her eyes, he has doubts regarding his previous suspicions that she is more than she seems. Meanwhile, Molly is able to learn the location of the Red Bull's lair from a talking cat.
Molly, Schmendrick, and Amalthea are joined by Lír as they enter the bull's den, but Haggard attempts to trap them by destroying the way they came in. Schmendrick reveals Amalthea's true identity to Lír after explaining what they are looking for. Lír is unmoved and says that he loves her anyway. This makes Amalthea want to abandon the quest and marry Lír, but Lír dissuades her. The Red Bull appears, but is no longer deceived by Amalthea's human form and chases after her. As Lír struggles to protect her, Schmendrick turns Amalthea back into the Unicorn, but she is unwilling to leave Lír's side. The Bull drives her toward the ocean just as he earlier drove all the other unicorns, but she manages to run away and the Red Bull gives chase. Lír tries to defend her, but is killed by the bull. Enraged, the Unicorn turns on the Bull and forces him into the sea. Carried on the white surf of incoming tides, the other unicorns emerge en masse from the water, causing Haggard's castle to collapse into the sea as they rush past, with Haggard falling to his death.
On the beach, the Unicorn magically revives Lír before departing for her forest. Schmendrick assures Lír that he has gained much by winning the love of a unicorn, even if he is now alone. He departs to start anew. The Unicorn returns to say goodbye to Schmendrick, who laments he has done her wrong by burdening her with regret and the taint of mortality, which could make her unable to rejoin her kind in the forest. She disagrees about the importance of his actions, as they helped them to restore unicorns to the world; though she is the only unicorn to feel regret, she is also the only unicorn to know love. Schmendrick and Molly watch the Unicorn depart for her home in the woods.Mia Farrow as the Unicorn / Lady Amalthea, the eponymous "last unicorn" who, in her search for the other unicorns, is transformed into a young woman and learns about regret and love.
Alan Arkin as Schmendrick, a magician who accompanies the Unicorn on her quest to find others like her. Beagle commented that he was a bit "disappointed" by the way Alan Arkin approached the character because it seemed "too flat".
Jeff Bridges as Prince Lír, King Haggard's adopted son who falls in love with Lady Amalthea. Although he is later told by Schmendrick that she is a unicorn, his feelings for her remain.
Tammy Grimes as Molly Grue, the love of Captain Cully who joins Schmendrick and the Unicorn. While explaining that there was no particular reason that he did not write a detailed background for Molly Grue's character, Peter S. Beagle stated that he has "always been grateful" to Grimes because she "brought such vocal life to the character that she covered things I didn't do."
Robert Klein as The Butterfly, the creature that gives the Unicorn a hint as to where to find the other unicorns.
Angela Lansbury as Mommy Fortuna, a witch who uses her illusory magic to run the Midnight Carnival, which showcases mythical creatures that are, in truth, just normal animals. Later, the harpy Celaeno, one of the two real mythical creatures, kills her and her henchman, Ruhk.
Christopher Lee as King Haggard, the ruler of a dreary kingdom, who has never been happy, save for when he looks at unicorns. Beagle described Lee as "the last of the great 19th Century actors, and either the most-literate or second-most literate performer I've ever met." When Lee came in to work, he brought his own copy of the novel wherein he took note of lines that he believed should not be omitted. Lee, who was fluent in German, also voiced King Haggard in the German dub of the film.
Keenan Wynn as Captain Cully, the leader of a group of bandits.
Wynn also voices The Harpy Celaeno, a real harpy that was captured by Mommy Fortuna, freed by the Unicorn, and kills Mommy Fortuna and Ruhk out of vengeance for trapping her.
Paul Frees as Mabruk, King Haggard's court magician who is replaced by Schmendrick.
René Auberjonois as the Skull that guards the clock that serves as an entryway into the Red Bull's lair. Beagle praised Auberjonois' performance, saying "he could have played any role in that movie and I would have been happy ... He's that talented."
Brother Theodore as Ruhk, a hunchback who works for Mommy Fortuna. He along with Mommy Fortuna are killed by the Harpy Celaeno.
Don Messick as the Cat, an old cat who gives Molly hints on finding the Red Bull.
Nellie Bellflower as the Tree, a tree that speaks and falls in love with Schmendrick after he casts the wrong spell on it.
Edward Peck as Jack Jingly, Cully's Men
Jack Lester as Hunter #1, Old Farmer, Cully's Men
Kenneth Jennings as Hunter #2, Cully's Men
Produced and directed by Arthur Rankin Jr., Jules Bass
Screenplay/based on the novel by Peter S. Beagle
Executive producer: Martin Starger
Animation coordinator: Toru Hara
Continuity animation: Tsuguyuki Kubo
Backgrounds: Minoru Nishida, Kazusuke Yoshihara, Mitsuo Iwasaki
Production designed by Arthur Rankin Jr.
Associate producer: Michael Chase Walker
Music and lyrics by Jimmy Webb
Songs performed by America
In charge of production: Masaki Iizuka
Character design: Lester Abrams
Continuity and animation direction: Katsuhisa Yamada
Key animation: Kazuyuki Kobayashi, Hidemi Kubo, Tadakatsu Yoshida
Animation: Yoshiko Sasaki, Masahiro Yoshida, Kayoko Sakano, Fukuo Suzuki
Camera: Hiroyasu Omoto
Editor: Tomoko Kida
Sound effects: Tom Clack, Kiyoshi Ohira
Assistant animation coordinator: Kiyoshi Sakai
Additional storyboard sequences: Don Duga
Tapestry designer: Irra Duga
Production coordinator: Lee Dannacher
Orchestrators: William McCauley, Matthew McCauley
Additional orchestrators: Jimmy Webb and Elton Moser
Recording engineers: John Curcio, John Richards, Dave Iveland
Recording mixer: Donald O. Mitchell
Peter S. Beagle stated that there had been interest in creating a film based on the book "early on". Those who expressed interest included Lee Mendelson and Bill Melendez, though Beagle had been convinced by one of their partners' wives that they were "not good enough", as well as former 20th Century Fox animator Les Goldman. At the time, Beagle believed that "animated was the only way to go" with regard to the film, and had never thought of making it into a live-action film. Rankin/Bass had been the last studio that the film's associate producer, Michael Chase Walker, approached, and Beagle was "horrified" when he was informed that they had made a deal with Walker. Beagle stated that he has "…come to feel that the film is actually a good deal more than I had originally credited", and went on to say "There is some lovely design work – the Japanese artists who did the concepts and coloring were very good. And the voice actors do a superb job in bringing my characters to life…"
While Rankin/Bass provided the film's dialogue and story based on Beagle's work, the animation was done by the studio Topcraft. The studio would later be hired by Hayao Miyazaki to work on the 1984 animated film Nausicaä of the Valley of the Wind, and their core members eventually went on to form Studio Ghibli. According to Beagle, the final film ended up being "remarkably close" to his original script, although one scene at the end involving an encounter with a princess was "animated but eventually cut."
The musical score and the songs were composed and arranged by Jimmy Webb, and performed by the group America and the London Symphony Orchestra, with additional vocals provided by Lucy Mitchell. The Last Unicorn soundtrack was recorded at De Lane Lea Studios in Wimbley, England in 1982. The album was released in Germany in 1983 by Virgin Records, but has not been released in the United States; it includes the film score's symphonic pieces. In his review for AllMusic, James Christopher Monger called it, "an appropriately somber and sentimental blend of fairy tale motifs and dark, Wagnerian cues".
The Last Unicorn premiered in 648 theaters in the United States on November 19, 1982, and earned $2,250,000 on its opening weekend.
The film was released on VHS by CBS/Fox Video in 1983, Playhouse Video in 1985, J2 Communications/ITC Home Video in 1988, and Family Home Entertainment in 1994.
The first U.S. DVD, released by Lionsgate on March 16, 2004, was made from poor-quality pan-and-scan masters. Upon the release of this DVD, Conlan Press lobbied Lionsgate "to do something about it." Lionsgate licensed the German video masters and audio mix and came up with a "25th Anniversary Edition" DVD which was released in North America on February 6, 2007. It has audio and visual quality superior to the original U.S. release, and is in 16:9 widescreen format, but has several swear words edited out, and as a result of being taken from PAL masters, plays 4% faster than the original film, resulting in a slightly higher audio pitch than normal. The new DVD edition includes a featurette with an interview with the author, as well as a set-top game, image gallery, and the original theatrical trailer. As of October 2011, over 2,500,000 copies of the DVD have been sold.
On February 11, 2011, Lionsgate released The Last Unicorn on a Blu-ray/DVD combo pack, which reinstated the original unedited audio track with swear words retained as in the U.S. theatrical release. The edited audio track (from the earlier "25th Anniversary Edition" DVD) was also included as an optional audio track.
On June 9, 2015, Shout! Factory released new Blu-ray and DVD versions of The Last Unicorn entitled "The Enchanted Edition". This edition was transferred from a new widescreen 2K digital master; includes the original uncensored audio as well as a commentary track with Peter S. Beagle, associate producer Michael Chase Walker, tour producer Connor Freff Cochran, and Conlan Press team members; highlights from the Worldwide Screening Tour; a new True Magic: The Story of the Last Unicorn featurette; animated storyboards; and the original theatrical trailer.
In a New York Times review, Janet Maslin called The Last Unicorn "an unusual children's film in many respects, the chief one being that it is unusually good. [...] features a cast that would do any live-action film proud, a visual style noticeably different from that of other children's fare, and a story filled with genuine sweetness and mystery." and said that "no one of any age will be immune to the sentiment of the film's final moments, which really are unexpectedly touching and memorable". Beagle himself called the film "magnificent" in comparison to J.R.R. Tolkien's The Lord of the Rings, for which he also wrote the screenplay. As of 2017, the film has a 63% rating on Rotten Tomatoes.
A 1982 Variety reviewer praised the script and voice acting but was not impressed by the film's animation. "However vapid the unicorn may appear to the eye, Mia Farrow's voice brings an almost moving plaintive quality to the character." The review also praised the vocal talents of Arkin, Lee, and Frees.