Kristen Stewart Apologizes for Cheating on Robert Pattinson

Kristen Stewart has been a tabloid fixture for as long as the Twilight film franchise has been playing in theaters -- specifically, for her offscreen relationship with co-star and beau Robert Pattinson, the saga's most-drooled-after matinee idol.

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But until now, the quirky and red carpet-shy actress has never been the subject of anything remotely scandalous with respect to her personal life.

In a shocking confession, Stewart, 22, is publicly apologizing for cheating on Pattinson with the married Rupert Sanders, who directed her and Charlize Theron in Snow White and the Huntsman. 

"I'm deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected," she said Wednesday in a statement to People magazine. "This momentary indiscretion has jeopardized the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I'm so sorry."

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Sanders, 41, who has two kids with his wife, model and actress Liberty Ross, released a statement to THR, saying: "I am utterly distraught about the pain I have caused my family. My beautiful wife and heavenly children are all I have in this world. I love them with all my heart. I am praying that we can get through this together."

Stewart's rep did not respond to THR's request for comment.

Stewart graces the cover of this week's edition of Us Weekly for her affair with Sanders, who.The magazine has published photos of a "steamy rendezvous" between Stewart and Sanders. 

People followed up the report earlier Tuesday, citing sources as saying: "Kristen is absolutely devastated. It was a mistake and a complete lapse in judgment."

The Twilight Saga: Breaking Dawn -- Part 2 arrives in theaters Nov. 16. Earlier this month, the cast including Stewart, Pattinson and Taylor Lautner appeared at Comic-Con in San Diego to promote the final installment of the franchise.

"Kristen’s done such a good job across this whole franchise being this perfect, awkward, clumsy, relatable girl," Lautner said on the film's panel. "And she’s now transformed herself into this sleek, sexy vampire. It was very impressive."