Her longtime assistant, Seton Hawkins, confirmed her death but did not give a cause.
Like her husband of many years, the acclaimed pianist Abdullah Ibrahim, Ms. Benjamin became well known only after leaving South Africa. The two moved to Europe in 1962, shaken by events like the Sharpeville massacre two years earlier. Later they declared their support for the African National Congress, living in exile in New York and raising both money and awareness for the antiapartheid cause.
During a career of more than 50 years, Ms. Benjamin upheld a style of elegant composure and deliberative understatement, singing in a honeyed, faintly smoky mezzo-soprano. She occasionally undergirded her music with the carnival-influenced shuffle beat known as Cape Town rhythm. But even at buoyant tempos she favored an unhurried, elastic, balladlike delivery, drawing out lyrics and often scooping up to a note.
Reviewing a 1986 performance for The New York Times, Jon Pareles wrote that Ms. Benjamin "treated the songs as languorous phrases floating above the beat, with carefully turned glides and curves and delicate shifts of timbre a graceful, somber, pared-down approach."
Beatrice Bertha Benjamin was born in Johannesburg on Oct. 17, 1936. Her father, Edward Benjamin, had come to South Africa from St. Helena, a British colonial island in the South Atlantic; her mother, Evelyn Henry, was of Mauritian and Filipino descent. Her parents divorced when she was a small child, and she was raised by her paternal grandmother, known as Ma Benjamin, in a suburb of Cape Town.
She began singing in nightclubs as a teenager, and met Mr. Ibrahim, then known as Dollar Brand, in her 20s. They began working together, recording her unreleased first album, "My Songs for You," in 1959. (She went by Beatty Benjamin at the time.)
One evening in 1963, not long after the couple had settled in Zurich, Ms. Benjamin attended a concert there by the Duke Ellington Orchestra and implored Ellington to hear the Dollar Brand Trio at a club. Impressed by what he had heard, Ellington arranged to record the group in Paris. He did the same for Ms. Benjamin, producing both albums himself for Reprise.
"Duke Ellington Presents the Dollar Brand Trio" was soon released, but the label shelved Ms. Benjamin's album, "A Morning in Paris." She did, however, reap the benefit of Ellington's imprimatur when she appeared with his orchestra at the 1965 Newport Jazz Festival. (She sang "Solitude," an Ellington ballad she had recorded for the album.)
Ms. Benjamin and Mr. Ibrahim were married in 1965. When they converted to Islam three years later, he changed his name to Abdullah Ibrahim (he was born Adolph Brand), and she adopted the name Sathima Ibrahim, using Sathima Bea Benjamin professionally.
They had a son, Tsakwe, now a pianist in Cape Town, and a daughter, Tsidi, now the underground rapper known as Jean Grae. Both survive her, as do her two sisters, Edith Green and Joan Franciscus.
In 1977, after years of itinerant living, the Ibrahim family planted roots in New York, taking an apartment in the Chelsea Hotel. Ms. Benjamin continued to live there even after Mr. Ibrahim returned to South Africa in 1990, initiating their separation. She moved back to Cape Town herself in 2011, the year their divorce was finalized.
Also that year, Ms. Benjamin published a book with the South African musicologist Carol Ann Muller, "Musical Echoes: South African Women Thinking in Jazz." Among other things, the book recalls the hardships of state segregation.
Ms. Benjamin didn't shy from that subject as an artist: her albums, beginning with "African Songbird" in 1976, include original songs of clear political subtext. One album she released on the Enja label, in the late 1980s, opens with a song called "Winnie Mandela Beloved Heroine." Most of Ms. Benjamin's other albums were released on her own label, Ekapa. "A Morning in Paris," long thought to be lost, was finally issued in 1996, from a copy made by the album's recording engineer.
Two weeks before she died, Ms. Benjamin received a lifetime achievement award at the Standard Bank Joy of Jazz festival in Johannesburg.