Katherine "Kay" Corleone (née Adams) is a fictional character originating in Mario Puzo's 1969 novel The Godfather.

[2] In the opening wedding scene of The Godfather, Kay is the only female character who "speaks more than a few lines, and she only then asks questions",[3] which serve as a means to provide exposition about the male members of the family who dominate the story.

In a 50-year retrospective of the original film, The Independent said that "female characters are either relegated to the sidelines or treated very badly", and that "Keaton registers very strongly as Michael Corleone's girlfriend Kay Adams in the early scenes – but then she all but disappears for two hours before re-emerging only in the final chapters".

[5] Kay's character arc across films has been described as "plausible", portraying her initial concern, and then increasing estrangement from Michael Corleone, as she confronts the moral and emotional toll of his criminal empire.

In The Godfather Part II, her alienation intensifies as she challenges Michael's loyalty to the family's Sicilian traditions and ultimately separates from him after revealing her abortion of their child.

By The Godfather Part III, Kay is remarried, and more aggressively confronts Michael over his hypocrisy while seeking to shield their children from his influence.

As a non-Italian, she is an outsider to the Corleones' world, and embodies Michael's initial desire to live a life separate from his family's.

In the novel, the other guests notice how Kay's manner is freer than what is expected from an unmarried woman in Italian traditionalist culture.

Michael flees to Sicily, where he falls in love with and marries a young local woman, Apollonia Vitelli (Simonetta Stefanelli).

At the beginning of The Godfather Part II (set in 1958–60), Kay lives with Michael at his Lake Tahoe compound, and is pregnant with the couple's third child.

On the night of Anthony's First Communion, assassins machine gun Michael and Kay's bedroom; the couple barely escape unharmed.

During the U.S. Senate hearing on organized crime that is being held in Washington D.C., Kay sits behind Michael, supporting him while he testifies falsely about his business activities.

Enraged, Michael strikes Kay and takes custody of their children, banishing her from the family; the two separate soon afterward.

Kay supports his decision, but Michael wants his son to finish his studies or go into the "family business" (putatively a legitimate charitable foundation, but still involved in underworld activities).

Michael survives another attempt on his life, but later suffers a diabetic stroke, after which Kay visits him in the hospital, and they begin to repair their relationship.

[7] Keaton read with both James Caan and Martin Sheen before Al Pacino was finally confirmed for the role of Michael.

[8] One report noted that "Keaton said she always felt like an outsider in the movie—a similarity she shared with Kay, who is literally left with a door closing in her face at the end of the first film".