Severine (Catherine Deneuve) is a wealthy young newlywed who's eager to live life to the fullest. Although she loves her husband, Severine can't bring herself to be intimate with him. To sate her physical desires, she indulges in erotic daydreams, often blurring the line between reality and fantasy. When that's not enough, she begins frequenting a classy Parisian brothel, working as a prostitute while remaining celibate within her marriage.
Don Jaime lives alone in his manor. His wife died from a heart attack on the wedding night. He has paid the gift and education so that his wife's niece Viridiana could become a nun, and wants her to visit him for a few days before she takes her final vow. She strikingly resembles her aunt and is persuaded to take on her wedding dress. Then he asks her to marry him. When she refuses, sleeping pills are put in her coffee. Jaime only decently fondles her. One the next day she leaves but is brought back by the police. Jaime had made a trap that might lead to another marriage. He acknowledges his "bastard" son Jorge, writes a will making his manor the common property of him and Viridiana, and hangs himself. Jorge starts modernising agricultural methods. Viridana gives free food and housing to many beggars. When Jorge and Viridiana must go away to see a lawyer, the beggars succeed in entering the locked great house. They make a banquet, but eventually beat asunder many things. When the owners return, most beggars leave the house forever. But one of them binds Jorge to a wall-cupboard and tries to rape Viridiana. Jorge promises another beggar money if he kills the rapist. He does so. One later evening when all is calm Viridiana goes to Jorge.
Just after boarding a train, much to the surprise of his fellow passengers, a man pours a bucket of water over a young girl on the platform. Over the next few hours he explains (and we see in flashback) how he became obsessed by her (so much so that he failed to notice that she was played by two different actresses, representing different sides of her personality), and how she tantalized him, but would never allow him to satisfy his desire for her...