The breakup comes after months of speculation that the "Poker Face" singer, 30, and the "Chicago Fire" actor, 35, were on the outs, reported E! online.
"They want to keep it private. It's heartbreaking," a source said.
The songtress released a statement following her breakup.
"Taylor and I have always believed we are soulmates. Just like all couples we have ups and downs, and we have been taking a break," Gaga wrote on Instagram with a black and white photo of the pair with their arms wrapped around each other's shoulder.
Last week-on Kinney's birthday-Gaga was photographed without her engagement ring. When she performed at an orphanage in Mexico earlier this week, the ring was again missing.