Diane Keaton plays Kay Adams in The Godfather.
Kay is introduced as Michael Corleone’s non-Italian-American girlfriend at the wedding of his sister Connie. She initially stands outside the family’s criminal world, giving the audience a perspective on the Corleones’ private lives and public image.
Michael’s relationship with Kay changes after he returns from Sicily. They marry, but Kay becomes increasingly troubled by Michael’s role as head of the family. Their relationship is central to the film’s emotional ending, when the door to Michael’s office closes between them.
Keaton returned as Kay in The Godfather Part II and The Godfather Part III. A common mix-up is confusing Kay with Connie, Michael’s sister, who is played by Talia Shire. Keaton’s performance also helped establish Kay as one of the trilogy’s most important non-criminal characters.