"To address speculation - myself and Rita ended our relationship some time ago," he wrote. "She is a beautiful, talented woman & I wish her all the best."
Calvin Harris and RIta Ora at the Grammys in 2014
Rita, who began dating Calvin in May 2013, has remained silent about the news on her own Twitter account.
Initial speculation that Rita and Calvin were no longer an item began at the beginning of the year when the I Will Never Let You Down singer stopped following her boyfriend on Instagram. Fans of the couple were later surprised to see Dumfries-born Calvin partying with other women.
Rita and Calvin, whose real name is Adam Richard Wiles, were last seen together at a taping of Watch What Happens Live in New York City at the end of April.
Discussing falling in love with the DJ, R.I.P singer Rita said: "There are so many things. The fact that he got something out of me that I never thought I had. Yes, like falling in love. I just didn’t think I had it. I’d never experienced it before. And I was just like in the wilderness, thinking, “Will it ever happen?"