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.
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.