Lorraine Graves, a ballerina known for her willowy frame and majestic grace who starred as a principal dancer for the groundbreaking Dance Theater of Harlem for nearly two decades, died on March 21 in Norfolk, Va. She was 66.

Her nephew Jason Graves said the cause of her death, in a hospital, was yet to be determined.

Ms. Graves broke barriers — not only as a celebrated dancer for a multiracial company that showcased African American excellence in a traditionally European art form, but also, at a towering 5-foot-10 ½, as an exceptionally tall one.

For a female dancer, “five foot four, five foot six is considered tall,” Virginia Johnson, a former principal dancer and artistic director for the Dance Theater of Harlem, said in an interview. “Because once you get on pointe, you’re adding another six inches to your height, and so having a partner who’s tall enough to partner you is an issue.”

Fortunately, the company had plenty of tall male dancers. That allowed Ms. Graves an opportunity to leverage her unique physicality, which over the course of her career she showed off in performances around the world, including before world leaders like Mikhail Gorbachev and Nelson Mandela.

“She was commanding,” Ms. Johnson said. “She had a lot of power as a dancer, and had a magnificent jump.”

Dance Theater of Harlem was formed in 1969 by Arthur Mitchell, an international star who was the first African American principal dancer at New York City Ballet, with Karel Shook, a renowned ballet master who had trained Mr. Mitchell.

The company was conceived as an artistic response to the assassination of the Rev. Dr. Martin Luther King Jr. the previous year. Mr. Mitchell recalled with pride in a 2018 interview with The New York Times that “I actually bucked society, and an art form that was three, four hundred years old, and brought Black people into it.”

Even so, progress for African Americans was hard won in the world of ballet: George Balanchine, the hallowed choreographer and a founder of City Ballet, had once said that a ballerina’s skin should be the color of a peeled apple.

When Ms. Graves joined the company in 1978, “there were some African American dancers in the world,” she said at a 2019 talk at the Alabama School of Fine Arts in Birmingham, but “we didn’t really hear about them.”

Therefore, she added, “All the little Black girls that wanted to be ballerinas migrated to Dance Theater of Harlem,” which gave “those of us who wanted to be ballerinas a platform to show that we could be classical ballet dancers, not modern dancers, not jazz dancers.”

While it was classical in focus, the company never hesitated to reshape the great ballets on its own terms.

One of Ms. Graves’s many star turns came in the Dance Theater of Harlem’s 1984 production of “Giselle,” a reimagined Creole version of the landmark 19th-century French ballet, set in the American South of the 19th century. “The choreography was the same,” Ms. Graves said. “But our Giselle was transposed out of Austria to the bayous of Louisiana, so it made it relevant to us at the time.”

Reviewing that production in The New York Times, Anna Kisselgoff praised Ms. Graves’s performance as the Queen of the Wilis, ghostly maidens who had died of broken hearts. “The corps, undefined in period,” she wrote, “suggests a vampirish sisterhood brilliantly led with vigor by Lorraine Graves’s Amazonian Myrtha.”

Ms. Graves was also known for her spellbinding performances as the Princess of Unreal Beauty in Stravinsky’s “Firebird,” which she performed on multiple national tours with the company, including a 1982 performance at the John F. Kennedy Center for the Performing Arts in Washington that was seen nationally on public television.

Her performances in Balanchine’s “The Four Temperaments” drew raves. Ms. Graves “was a tigerish ‘Choleric,’” Jennifer Dunning wrote in a 1987 review in The Times, “with those long, powerful arms of hers coming into play in the ballet’s final moments.”

Lorraine Elizabeth Graves was born on Oct. 5, 1957, in Norfolk to Tom and Mildred Graves. As a child, she said in a 2020 video interview with The Virginian-Pilot, “I remember watching New York City Ballet’s ‘Nutcracker’ on TV, and I would try to imitate what I saw them doing.”

When she was 8, her mother arranged an audition at a prestigious local ballet academy, where she became the first African American student. “I never thought about color,” she later said. “I just thought about being the best that I could be.”

Her single-minded dedication carried into her early years at Lake Taylor High School in Norfolk, where she often found herself stooping to fit in with other girls because of her height.

When she was about 16, she detoured into what she called her “boy era,” pulling back from rigorous year-round training to date and go to football games like other students. But “once that period was over,” she said in a 1982 interview with The Austin American-Statesman, “my senior year was total dedication, and it’s been that way ever since.”

After graduating in 1975, Ms. Graves enrolled in Indiana University Bloomington, where she completed a four-year program for a bachelor’s degree in ballet in only three years.

From there it was on to New York City, where she quickly joined Dance Theater of Harlem and rose to principal dancer within a year.

Before long, she also assumed her longtime role as the company’s ballet mistress (the title is now rehearsal director). In that position, she served as the top assistant to the company’s artistic director, preparing the dancers for performance down to the most intricate details, including counts, spacing and dynamics.

“She had a photographic memory,” Ms. Johnson said. “She knew exactly what every single dancer was doing, principal or corps de ballet, and when they were doing it.”

Ms. Graves is survived by her brother, Tommy Graves III.

She retired from the company in 1996 after being diagnosed with lupus. But she continued to teach ballet for decades, including 20 years at the Governor’s School for the Arts in Virginia.

Still, she maintained strong ties with the Harlem company. In 2012, she accompanied Mr. Mitchell to Russia, where she had toured with the company 24 years earlier, to assist with lectures and instruction at top ballet schools including the Bolshoi Ballet Academy.

In her talk at the Alabama School of Fine Arts, Ms. Graves looked back on the 2012 trip with pride: “How many little African American girls from Norfolk, Virginia do you know have gone to Moscow and St. Petersburg and taught the Russians ballet?”