Most of the novel is set during the time of the Risorgimento, specifically during the period when Giuseppe Garibaldi, the leader of the famous Redshirts, swept through Sicily with his proletariat army known as The Thousand.
As the novel opens in May 1860, Garibaldi's Redshirts have landed on the Sicilian coast and are pressing inland; they will soon overthrow the Kingdom of the Two Sicilies and incorporate it into the unified Italian Kingdom under Victor Emmanuel. The plot focuses upon the aristocratic Salina family, which is headed by Prince Fabrizio. Don Fabrizio is the patriarch of the family as well as the keeper of its strict code of conduct and Roman Catholic ritual. Prince Fabrizio finds marriage with his overly puritanical wife to be physically unsatisfying, and thus keeps a series of mistresses and courtesans as well as indulging in his hobby of amateur astronomy. He is drawn to his nephew Prince Tancredi Falconeri whom he sees as having noble qualities. This affection is somewhat diminished when he discovers that Tancredi has joined Garibaldi's Redshirts. On a trip to the Salina estate in the town of Donnafugata the Prince learns that the mayor, Don Calogero Sedara, has become wealthy through dodgy business transactions and political influence and that his wealth now rivals that of the Salinas. When Sedara introduces his extraordinarily beautiful daughter, Angelica, Tancredi is smitten with her, to the dismay of the Prince's daughter Concetta, who loves Tancredi. Although aware of his daughter's feelings, the Prince accepts the inevitable and helps arrange Tancredi's betrothal to Angelica. The two pass a blissfully innocent period of engagement.
Fabrizio is offered the position of a Senator in the new Italian state but turns it down. Angelica is introduced to Palermo society at a sumptuous ball and despite her background slips easily into the role of future countess. The narrative then jumps forward by two decades and finds Prince Fabrizio on his deathbed, surrounded by family. The Prince considers that he will be the last true prince of the Salinas, the last leopard. A final chapter takes place in 1910 when Concetta, now seventy, is living in the family home with two of her sisters.
