Keira Knightley’s Broadway debut nearly derailed on her first night of previews when a lovelorn loon shouted from the audience that he wanted to marry her — and flung a bouquet of roses at her feet.

“Christ was born a virgin!” Landon Rust, 29, of Texas, hollered about 15 minutes into Thursday night’s performance, ¬according to witness accounts.

“Keira, none of this is real!” he shouted as he leaned over a mezzanine railing at the Studio 54 theater on West 54th Street.

“I love you! Keira, marry me!”

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The British beauty gamely carried on with the opening scene of the play, “Thérèse Raquin,” based on a novel by Emile Zola, as Rust waited in vain for her response.|

“Five seconds is too long to wait for a response!” Rust then ranted. “Five seconds is a slow burn!”

Knightley and her co-stars kept on going while theater security converged on Rust and led him out. But not before he broke free, rushed to the mezzanine railing and hurled a huge bouquet of flowers over the orchestra seats.

Rust was taken from the theater in handcuffs, and driven to St. Luke’s Hospital after complaining of stomach pains, law-enforcement sources said. He was given a summons for misdemeanor harassment.

Click here to read more in the New York Post.