The actress passed away on Tuesday (June 26), according to Variety.
Lucille Ball and Desi Arnaz's daughter Lucie Arnaz also confirmed Singleton's death while paying tribute to Nora Ephron on her Facebook page.
Lucie wrote: "A day of saying hasta luego to two great ladies, Nora Ephron and Doris Singleton. May they both fly swiftly heavenward and enjoy a blissful rest for jobs well done down here. They were loved and appreciated and will be missed."
The actress got her start in show business by dancing with the New York City Ballet for three seasons and broke into the television industry after a stint on radio.
Singleton made ten appearances on I Love Lucy as Lucy Ricardo's near-sighted nemesis Carolyn Appleby in the 1950s.
Gunsmoke, The Twilight Zone, The Dick Van Dyke Show and Hogan's Heroes are among Singleton's television credits. She also reunited with Ball on The Lucy Show for two episodes in 1966 and 1967.
Singleton was married to producer Charles Isaacs, who died in 2002.
Watch Doris Singleton in a clip from I Love Lucy below: