NEW YORK, NY.- Lynn Seymour, a ballerina who was widely hailed over her long career as one of the greatest of all dance actors, died on March 7 in London. She was 83.

Her death was announced by the Royal Opera House Covent Garden, where she had performed for many years as a principal, and later as a guest, of its resident company the Royal Ballet. No cause was given.

The most radically original dancer in British ballet history and a star on both sides of the Atlantic, Seymour inspired international choreographers of successive generations.

Canadian born, she became a choreographer, artistic director of two European ballet companies and a screen actress. But it was as a dancer that she astounded audiences in many countries with her dramatic intensity, seemingly boneless fluidity of movement, physical abandon and innovative characterizations of famous roles.

Seymour closely watched the leading actors of her day, including Joan Plowright and Judi Dench. In turn, she was praised by Dench (who called her “one of my heroines”), Michael Gambon (who cited a 1977 Seymour-Mikhail Baryshnikov “Romeo and Juliet” as the greatest dance performance he had ever seen), Ian McKellen and many more renowned actors.

In London, she risked royal disapproval by dancing scandalous roles at prestigious galas. In newspapers, she spoke up against the stuffiness of ballet. In 1999, Baryshnikov, remembering his three 1977 performances as Romeo to her Juliet, recalled her gift for reckless rapture onstage.

For 40 years Seymour was a muse to multiple choreographers. Four of the many vehicles created for her were three-act productions; she found the challenge of tracing a vast theatrical arc over a three-act work supremely fulfilling. She also created roles for dancers William Forsythe, John Neumeier, Ian Spink, Glen Tetley and others.

Berta Lynn Springbett was born on March 8, 1939, in Wainwright, Alberta, the second of two children of Ed Springbett, a dentist, and Marjorie (McIvor) Springbett, a homemaker. (In 1954, her brother, Bruce Springbett, a sprinter, represented Canada in the 220-yard event at the Commonwealth Games in Vancouver, British Columbia.)

As a teenager in 1953, when the Sadler’s Wells Ballet was on one of its biennial tours of North America, Seymour successfully auditioned for a place at its London school. Her gifts were quickly recognized by the company’s resident choreographer, Frederick Ashton: She displayed keen musicality, a rich-toned lyricism, an exceptionally supple torso and an unusually rounded carriage of the arms (port de bras) that gave her dancing qualities that could seem both Romantic and Russian. The singular fascination she inspired stemmed from an intensely romantic classicism that was imbued with a searchingly modern spirit.

In 1956, at age 17, she joined the Covent Garden Opera Ballet. There the choreographer Kenneth MacMillan chose her for a leading role in one of his first ballets, and the two collaborated for the next 20 years, challenging the perceived nature of ballet. Together (“living in each other’s pockets,” she once said) they followed the new developments in British theater and film. In 1960, he made her the young protagonist of “The Invitation,” in a role that involved teenage sensuality and the trauma of sexual assault.

Seymour began to dance Odette-Odile, the protagonist of “Swan Lake,” in 1959, the same year she became, at only 20, a principal of the Royal Ballet’s touring company. In 1961, Ashton made her the heroine of his two-act romantic comedy “Les Deux Pigeons” (soon renamed “The Two Pigeons”), which takes its vulnerable two young lovers through heartbreak before reaching a deeply affecting reconciliation.

Christopher Gable, a dancer with a new-generation informality of manner that complemented the Seymour style, partnered her in both “Invitation” and “Pigeons.” In 1962, she transferred to the Royal Ballet’s senior troupe, often called the Royal Ballet at Covent Garden.

In 1963, she married Colin Jones, a photographer and former dancer. The marriage was short-lived, ending after Seymour, by her account, terminated a pregnancy so that she could create the role of Juliet in a three-act “Romeo and Juliet” that MacMillan was commissioned to make. She had consulted her choreographer about ending the pregnancy but not her husband.

Seymour was later dismayed to learn that at the insistence of the Royal Ballet’s management, the title roles for the first night’s performance of “Romeo and Juliet,” in 1965, would be performed not by her and Gable, her Romeo, but by Margot Fonteyn and Rudolf Nureyev, then the world’s two most famous dancers.

Seymour danced MacMillan’s Juliet until 1978. Her willful Juliet was the opposite of Fonteyn’s poetically passive, wronged one. Her emotions were violent. Alone on the balcony, yearning for Romeo, she pressed her arms, shoulders and neck against pillars and a ledge, writhing passionately. (“That was my Judi Dench rip-off!” she said in 2000, remembering Dench’s 1960 Old Vic account of Shakespeare’s heroine.)

In 1966, when MacMillan was made artistic director of the Berlin Ballet, she moved with him to Berlin. There he made the one-act pure-dance “Concerto” (1966) and a dramatic “Anastasia” (1967), with Seymour in central roles. In 1968, she gave birth to twins, Adrian and Jerszy Seymour; Polish dancer Eike Walcz was the father.

In 1970, MacMillan returned to Covent Garden, succeeding Ashton as director of the Royal Ballet. Seymour went with him. In 1970, she was part of the illustrious first Royal Ballet cast of Jerome Robbins’ “Dances at a Gathering,” alongside, among others, Nureyev, Monica Mason, Antoinette Sibley, Anthony Dowell and David Wall.

Immediately after its first 12 Covent Garden performances, Seymour performed a world premiere in New York: “Flowers” (1971). The work, by choreographer and dancer Alvin Ailey, was about the dark side of fame, with ideas drawn from the lives of Judy Garland, Marilyn Monroe and Bessie Smith as well as Janis Joplin. Seymour entered smoking an enormous fake marijuana cigarette.

She later looked back on her Ailey experience as “my happiest time ever.” Ailey, like MacMillan, suited her radical spirit, pursuing dark dramatic truth at the expense of conventional loveliness.

Six months later, she danced another audacious world premiere: She and MacMillan turned their 1967 “Anastasia” (to music by modernist Czech composer Bohuslav Martinu, with untitled electronic music by Fritz Winckel and Rüdiger Rüfer) into the final act of a new three-act “Anastasia,” with the first two acts set to Tchaikovsky symphonies. In Act 1, Seymour as Anastasia, the tomboy daughter of Czar Nicholas II, entered on roller-skates.

By the third act, she was Anna Anderson, by then in a Berlin mental institution, insisting on her identity as Anastasia, piecing together her past after the traumas of the Russian Revolution. Seymour’s entire body language changed, astoundingly, from act to act.

Poor health, fluctuating weight, and depression had become intermittent parts of her life since the mid-1960s. In the 1970s, she married photographer Philip Pace, by whom she had her third son, Demian Pace, in 1974.

When she returned to dance after the childbirth, Nureyev, an especially close friend, helped her reach greater technical prowess than ever before. In 1975-76, Ashton created “Five Brahms Waltzes in the Manner of Isadora Duncan” and “A Month in the Country” for her. They became two of her most renowned roles.

As Isadora, she was barefoot, rapturous and revolutionary. As Natalia Petrovna in “A Month in the Country,” closely based on the Turgenev play, she was a sophisticated wife and chatelaine, guardian and mother, witty and charming, but also thunderstruck by a new love, perhaps her first true love, for her son’s 20-year-old tutor, Beliaev. Her character’s rapid psychological conflicts, comic and poignant, made this one of Seymour’s most brilliant dramatic roles.

In 1978, she created the role of Mary Vetsera in MacMillan’s three-act “Mayerling” at Covent Garden. Mary Vetsera is the final mistress of Crown Prince Rudolf of Austria, a partner who, understanding his obsession with sex and death, joins him in suicide. Seymour captured Vetsera’s fixation on Rudolf, her psychological darkness and her unhesitating eroticism.

From 1975 on, she also began to choreograph, experimenting with joining ballet and modern dance. In 1978, she left the Royal Ballet to become artistic director of the Munich Ballet. Health problems, however, arose again. She did not remain in Munich long. A third marriage, to Vanya Hackel, did not last. She announced her retirement from the stage in 1981.

But in 1988, at 49, Seymour surprised everyone by returning to dance with the English National Ballet, giving an intense and detailed performance of Tatyana in John Cranko’s three-act “Onegin.” She went on to perform with the postmodern group Second Stride and with Matthew Bourne’s company, then named Adventures in Motion Pictures. At least eight of her most important roles were filmed — some complete, some in excerpts — for television or cinema in her prime years.

She also acted on-screen in a 1983 Canadian television series, “The Little Vampire,” and in two films, Herbert Ross’ “Dancers” (1987) and Derek Jarman’s “Wittgenstein” (1993).

She is survived by her three sons; her brother, Bruce; and four grandchildren.

This article originally appeared in The New York Times.