The pair have decided to split after more than two years together.
Johnny Galecki and Kelli Garner have gone their separate ways according to reports from multiple sources.
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Galecki and Garner first stepped out together in 2012 and were spotted together on several high-profile red carpets, including Sunday's Emmy Awards ceremony and the Screen Actors Guild Awards last year. On Monday Galecki showed up solo to the Emmy Awards show, and attended a variety of parties afterwards with friends.
Reps for Galecki and Garner have not commented on the split.
The couple's break-up, however, was amicable and they are still "best friends," a source told Us Weekly.
Garner also joined Galecki at his costar Kaley Cuoco's New Year's Eve wedding to tennis player Ryan Sweeting. Afterwards the couple enjoyed a romantic getaway during the month of January in Mexico. Cuoco plays the actor's on-screen love interest on their highly-rated CBS sitcom.
Galecki, Cuoco and Jim Parsons signed new, three-year contracts with The Big Bang Theory earlier this month. The trio portray the characters Leonard, Penny and Sheldon in the hit TV series, and will reportedly earn $1 million per episode for the duration of their new contract.
Season 8 of "The Big Bang Theory" returns to CBS on September 22.