Earlier today, US reports claimed that K-Stew was having an affair with married Snow White And The Huntsman director Rupert Sanders - who is almost twice her age - with US Weekly publishing pictures of the pair together.
Now, the Twilight actress has admitted to the betrayal, apologising to Pattinson for her actions and confessing her love for the 26-year old.
In a statement obtained by People.com, Kristen said: "I'm deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected.
"This momentary indiscretion has jeopardised 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."
R-Pattz is yet to comment on the revelations, with Sanders' wife Liberty Ross posting a series of cryptic messages on Twitter, with one saying: "If you find it in your heart to care for somebody else, you will have succeeded."