Gorme died at a Las Vegas hospital of an undisclosed illness, said her publicist, Howard Bragman.
Since the mid-1950s, first as a soloist and then as part of the Steve and Eydie duo, Gorme sang pop hits, standards and show tunes while decked out in sequins and engaging in playful stage patter.
Her first album with Lawrence, "We Got Us," won a Grammy Award in 1960. The two also recorded separately, he making Billboard's top 10 with "Go Away Little Girl" in 1962 and she having a hit with "Blame It on the Bossa Nova" in 1963 and winning a Grammy for "If He Walked into My Life" in 1966. Together they starred in the Broadway musical "Golden Rainbow" in 1968.
"Eydie has been my partner onstage and in life for more than 55 years," Lawrence said in a statement. "I fell in love with her the moment I saw her and even more the first time I heard her sing. While my personal loss is unimaginable, the world has lost one of the greatest pop vocalists of all time."
Gorme (pronounced Gor-MAY) had been a singer with the Tex Beneke Band when Steve Allen hired her for his New York variety TV show in 1953. Lawrence was also part of the show's ensemble, and the two sang and acted in comedy sketches. They made the leap with Allen when his "Tonight" show was picked up by the NBC network in 1954, and for three years they were regulars on the late-night hit.
In 1957 Gorme appeared with comedian Jerry Lewis at the Palace Theatre on Broadway and with comic Joe E. Brown in Las Vegas. That December she married Lawrence in Las Vegas. They returned to television in 1958 with "The Steve Lawrence and Eydie Gorme Show" before Lawrence was called to the Army.
While he served for two years, she performed on her own, and upon his discharge in 1960 they resumed their professional partnership, billing themselves as Steve and Eydie.
"What has been the nature of their success?" Allen said in a 1996 Times story. "First, the fact that they are a couple has something to do with it. Secondly, they are damned good singers. And thirdly — this has both hurt and helped them — they concentrated for the most part on good music. This lost them the youthful audience, who prefer crap to Cole Porter's music. But it endeared them to people with sophisticated taste."
Gorme was born Aug. 16, 1928, in the Bronx, N.Y., to Sephardic Jewish immigrants. Her father was a tailor from Sicily and her mother was from Turkey. Before her singing career took off, Gorme worked as a Spanish-language interpreter.
In the mid-1960s she was pitched the idea of a Spanish-language recording. "Amor" and a follow-up album with the Mexican group Trio Los Panchos became hits in the U.S. and Latin America.
Gorme and Lawrence continued to perform on television variety shows, winning an Emmy for the 1978 special "Steve and Eydie Celebrate Irving Berlin," and on tour as a duo and opening for Frank Sinatra and others.
Besides her husband of nearly 56 years, Gorme is survived by their son David and a granddaughter. The couple's other son, Michael, who had a heart condition, died in 1986 at age 23.