KATY PERRY/DR. LUKE lose "DARK HOUSE" copyright infringement lawsuit

Katy Perry and Super-producer Dr. Luke have lost their copyright infringement lawsuit, brought upon by Christian rapper Flame, claiming her 2013 smash "Dark Horse" was a rip-off of his Grammy-nominated song "Joyful Noise".

Flame's music label uploaded the music video to YouTube way back in 2008, and it's since racked up millions of views. He says Katy jacked the underlying beat ... but she called BS, claiming there are NO meaningful similarities.

According to the suit ... Flame claims Perry also destroyed his reputation in Christian music circles because he's now associated with the anti-Christian witchcraft and imagery that's present in her "Dark Horse" music vid.

The case will now proceed to the damages phase -- AKA, when Katy finds out how much the loss will cost her.