The cause of her death Wednesday was not disclosed.
The New York-born scribe was a former WGA West vice president and past Academy of Motion Picture Arts and Sciences president.
Kanin began her five-decade-long screenwriting career in 1942 with the comedy "Sunday Punch," co-written with her longtime writing partner and husband, the late Michael Kanin, and Allen Rivkin.
Fay and Michael Kanin were one of the most successful wife-husband screenwriting teams in Hollywood, co-writing a string of screenplays for films such as "My Pal Gus," "Rhapsody," "The Opposite of Sex" and "Teacher's Pet" -- a Clark Gable-Doris Day comedy that earned an Oscar nomination in 1958 for Fay and Michael Kanin.
Later in her career, Kanin transitioned to television, emerging as a prolific writer-producer of some of the small screen's most distinguished projects, including TV movies such as "Tell Me Where It Hurts," which won two Emmy Awards in 1974, "Hustling" and "Friendly Fire," which won an Emmy in 1979.
She partnered with Lillian Gallo in 1980 to form the production company Kanin-Gallo, making TV movies such as "Letting Go" and "Fun and Games." She also penned and co-produced "Heartsounds," which was nominated for outstanding drama/comedy special in 1985.
A member of the Board of Trustees of the American Film Institute, she co-chaired AFI's Center for Film and Video Presentation, as well as chaired the National Film Preservation Board in Washington. Fay Kanin earned honors from the American Civil Liberties Union, the League of Women Voters, the American Women for International Understanding, and the Crystal Award of Women in Film, among other organizations.
"Known for her signature style and wit, Kanin remained an articulate industry spokesperson and leader on a variety of issues important to creative artists, including film preservation," the WGA said in a statement on its website.
The Academy of Motion Picture Arts and Sciences said Kanin was "committed to the Academy's preservation work and instrumental in expanding our public programming. A tireless mentor and inspiration to countless filmmakers, Fay's passion for film continues to inspire us daily."
Kanin is survived by her son, Josh; his wife Laurie; two grandchildren, Laurel and Jessica; two step-grandchildren, Michael and Eddy; and great-grandson, Justin.
Funeral services for Kanin will be held Sunday at the Hollywood Forever Cemetery in Hollywood.