The split news comes a few days after the actor was seen hanging out with singer Sela Vave in Los Angeles.
Katie seemed to confirm the split news over a recent dinner, Page Six said, quoting a source who overheard her saying, "What Jamie does is his business — we haven't been together for months."
According to Us Weekly, Katie was the one who pulled the plug.
The A-list duo was first linked in 2013, a year after Katie divorced Tom Cruise. For years, though, Katie and Jamie fought off speculation that they were an item, even after reported secret trysts and after photos of them kissing were published. Finally, Katie and Jamie debuted as a couple at the Met Gala in May.
After the debut, a source told E! News that they duo was "feeling more comfortable about being out in public together and not having to hide. They still don't want to have a public relationship, but it was a lot of effort to keep things under wraps and never be able to go out together. The burden of that has been lifted and they are feeling a lot more free to just go out and do normal things."