Angela Buxton, who broke racial barriers in the 1950s by forging a friendship and a formidable tennis partnership with Althea Gibson, the first Black player to win a championship at a major international tournament, has died at her home in Pompano Beach, Fla. She was 85.

Her death was announced by the Women’s Tennis Association, which said she died Aug. 14. Other sources gave the date of death as Aug. 15. The cause was not reported.

Gibson and Ms. Buxton were an early example of interracial harmony in sports, creating a dominant team to win the women’s doubles titles at the French and Wimbledon tennis championships in 1956.

Both women were considered outcasts in the genteel, mostly White sport of tennis. Ms. Buxton, who was British, had been denied membership and practice time at tennis clubs from London to Los Angeles because she was Jewish.

“The Southport club [in England] wouldn’t let me practice there,” Ms. Buxton told Britain’s Telegraph newspaper in 2019, “even though I was number one in England, so a member took me there as his guest. I took great delight in winning their tournament. As I rose up the rankings, the girls on the circuit ignored me . . . they never once invited me to join them for a meal.”

Gibson, who grew up in New York’s Harlem neighborhood, had a much harder struggle as the first African American player, male or female, to appear in any of tennis’s major international tournaments, when she competed in 1950 in what is now called the U.S. Open. The two players met in 1955 while on tour in India.

Ms. Buxton’s coach, Clarence “Jimmy” Jones, approached Gibson, who had a difficult time finding a doubles partner because of her race and sometimes-brusque manner, and asked if she would want Ms. Buxton as a partner. Shunned by other players, Ms. Buxton and Gibson formed a powerful and, for a brief time, unbeatable team.

“It never entered my head to do anything else except befriend her because we got on so well from the word go,” Ms. Buxton told the Philadelphia Inquirer in 2006. “She was much warmer than the English people. . . . We hit it off very well.”

In February 1956 they won the French indoor doubles title. That May, at the outdoor French Championships (now the French Open) in Paris, they were inseparable on the court and off.

“It was Angela and Althea, Althea and Angela, everywhere you looked,” author Bruce Schoen­feld wrote in his 2004 book “The Match: Althea Gibson and a Portrait of a Friendship.” “They were pictured dining together in a magazine snapshot, a white and a black sitting at table in the clubhouse at De Coubertin Stadium, laughing as if they were in on a joke that the rest of the world didn’t understand.”

Their friendship was cemented during the women’s singles semifinals, when they were competing against each other on opposite sides of the net. Late in the third and decisive set, Gibson’s bra strap broke. The crowd began to holler and whistle.

Ms. Buxton ran to Gibson’s side of the court, embracing her to keep her from being exposed. They walked together to the locker room, where Gibson changed her bra.

“I felt for Althea,” Ms. Buxton told Schoenfeld for his book. “I wanted her to do well nearly as badly as I wanted to do well myself.”

When they returned to the court, some officials called on Gibson to forfeit the match because she had left before it was completed and had received aid from another person. Ms. Buxton refused to claim victory on a technicality and demanded that the match be resumed.

Gibson went on to capture the final set, 6-4, and advanced to the finals. She defeated Britain’s Angela Mortimer in straight sets to become the first Black player to win a major tennis championship. The next day, Gibson and Ms. Buxton won the women’s doubles title.

In the 1956 Wimbledon championships, Ms. Buxton made the finals in the women’s singles, only to lose to American Shirley Fry. After beating Fry and her partner, Louise Brough, in the semifinals, Ms. Buxton and Gibson swept past Australians Fay Muller and Daphne Seeney in the finals, 6-1 and 8-6, to win the doubles title.

It was the last time the two would play together. Early in 1957, a serious wrist injury forced Ms. Buxton to retire from tennis at 22. That year, Gibson won both the Wimbledon and U.S. singles championships, the first Black person to win either title. She repeated the feat in 1958.

“On court she was very similar to Venus Williams,” Ms. Buxton told the Guardian newspaper in 2003. “She had the same look of disdain. You didn’t really know what was going on in her head. She was very tall and she was like a spider at the net — very difficult to pass or to lob. She was intimidating, just like Venus. And her expression never changed until the last ball had been hit.”

Gibson was at the peak of her abilities in 1958 when she retired from tennis, which at the highest level was strictly an amateur sport at the time. Today, players receive millions of dollars for winning Wimbledon or the U.S. Open. Gibson and Ms. Buxton got nothing but acclaim.

“They were teaching the world to do the right thing, no matter what,” tennis star Billie Jean King said in a 2013 documentary, “Althea and Angela: A Perfect Match.”

Angela Buxton was born Aug. 16, 1934, in Liverpool, England. Her father owned a chain of movie theaters.

To escape bombings during World War II, Ms. Buxton moved with her mother and brother to South Africa, where she took up tennis and befriended Black children — and developed an early sense of racial injustice after she was chastised by White neighbors.

Returning to Britain after the war, Ms. Buxton became one of the country’s top players. In the early 1950s, she and her mother moved to Los Angeles and lived near the Los Angeles Tennis Club, only to be denied membership because they were Jewish.

Ms. Buxton then trained at a public park under the tutelage of Bill Tilden, the preeminent men’s player of the 1920s — who was also a social outcast after having been jailed for molesting teenage boys.

After her playing career ended, Ms. Buxton opened a tennis academy in London and became a well-regarded journalist and the author of several books on tennis tactics.

In 1959 she married Donald Silk, president of the Zionist Federation of Great Britain. They had three children and, in the late 1960s, lived for a time on a kibbutz in Israel. The couple later divorced, after which Ms. Buxton had a long relationship with Jones, her former coach, until his death in 1986.

Ms. Buxton’s two sons predeceased her. Survivors include a daughter.

For years, Ms. Buxton divided her time between Florida and England. She periodically stayed in touch with Gibson, who had a short career in professional golf and later became a tennis coach and a public recreation official in New Jersey.

In 1995, a destitute and ailing Gibson called Ms. Buxton on the telephone.

“She said she was calling to say goodbye,” Ms. Buxton recalled in a 2019 interview with the New York Times. “She said she was going to kill herself. I said, ‘Now, wait just a minute.’ ”

Ms. Buxton wrote an article for a tennis magazine, pleading for help from Gibson’s fans. Almost immediately, checks began to arrive — hundreds of thousands of dollars, in all. Gibson was able to live in comfort until her death at age 76 in 2003.

“My legacy is definitely anti-racism because I was playing with a Black player who the audience didn’t really want to see,” Ms. Buxton said in the 2013 documentary.

She became Gibson’s tireless champion, seeking to keep her memory and example alive. Last year she was invited to the unveiling of a statue honoring Gibson at the site of U.S. Open in Flushing Meadows in New York City.

When she saw the sculpted likeness of her old friend and doubles partner, Ms. Buxton delivered a volley that could not be returned: “Doesn’t resemble her at all.”