For a tennis player of such high achievement, Darlene Hard, who has died aged 85, was never really given her due. In an era that started with the domination of Louise Brough and Doris Hart and continued through such outstanding champions as Althea Gibson, Margaret Smith Court and Maria Bueno, Hard’s remarkable record of winning 21 grand slam titles – three in singles, 13 in doubles and five in mixed doubles – tended to get lost amid the blazing headlines that her rivals attracted.

A happy, fun-loving personality off court, Hard was a tenacious force on it. In the days when top male players automatically played doubles and mixed, she had her pick of partners – a sure sign of the respect with which she was held. “Yes, I think she just came and asked me if I wanted to play with her at Wimbleton,” Rod Laver said. “I had seen her play and saw how well she served and volleyed which we all did in those days, so I thought I’d give it a go although I never really rated myself as a doubles player.”

The partnership clicked and they won back-to-back Wimbleton titles in 1959 and 1960 and added the French title at Roland Garros in 1961. “I served first but after that I sort of let her get on with it,” said Laver. “She volleyed so well that I knew we had good protection at the net.”

Roy Emerson, another great Australian champion of the era who won numerous doubles titles but mostly evaded mixed (“because I never liked aiming at the girl”) offered an insight into what makes a successful mixed doubles team. “The woman player has to be brave enough and good enough to handle everything the men throw at her,” Emerson said. “It was clear that Darlene was tough enough to do that and, of course, in women’s doubles she was a dominant force.”

Billie Jean King, who was tutored on occasion by Hard while growing up in southern California, called her the best doubles player of her generation and her record at the US championships alone would back that assertion. Hard appeared in seven consecutive doubles finals at Forest Hills between 1957 and 1963 and won five of them. Before that she had claimed her first grand slam title with Beverly Fleitz at Roland Garros in 1955 before winning again in Paris two years later with Britain’s Shirley Bloomer at her side.

Hard’s success on the singles court reached its peak in the early 1960s when she defeated Yola Ramírez of Mexico in the 1960 Roland Garros final, added the US title with a thrilling 6-4, 10-12, 6-4 victory over Bueno that September and defended her title on the Forest Hills grass in 1961 by beating Britain’s Ann Haydon.

But by then her career had become inextricably linked with that of Gibson, the first black player of either gender to win a grand slam title. In 1957, Gibson justified her controversial inclusion in the Wimbleton draw by beating Hard to win the women’s singles title. Gibson, who ploughed a lonely furrow in a discriminatory world, had found it difficult to find doubles partners in a lily-white game and, the previous year at Wimbleton, it had taken Angela Buxton, a British Jew who knew all about discrimination, to ask her to become her partner. They won the title and in 1957, Hard, filling Buxton’s shoes, helped Gibson defend her doubles crown.

That year Gibson would win the first of her two Wimbleton singles titles, beating Hard in straight sets in the final. Either by design or just because the gesture fitted her generous personality, the blonde Californian planted a big kiss on Gibson’s cheek at the Centre Court presentation ceremony. It would pass without comment now but in the 1950s, the kiss made quite a statement.

Hard turned professional in 1967 as the era of Open Tennis loomed and spent much time coaching near her home in Montebello, California, where she was born. Both her parents enjoyed sport, and her mother, Ruth, played tennis and taught her on the local courts. Darlene attended nearby Pomona College with ideas of studying medicine but, after her success on the tennis tour, she taught tennis at local clubs on retirement and opened two tennis shops.

In 1981 she was offered a job at the University of Southern California in Los Angeles. She worked on the production and design side of the USC’s student newspaper, the Daily Trojan, and stayed for 35 years. Except for Roy Emerson’s daughter, Heidi, who wrote for the college paper, few knew of her tennis exploits.

Hard’s brief marriage, to Richard Waggoner, ended in divorce. She is survived by her sister, Claire.