Michael Phelps and longtime girlfriend Nicole Johnson broke up last month after she moved from California to live with him in his hometown of Baltimore, Page Six can reveal.

The multiple gold-medal-winning Olympic swimmer and Miss California USA 2010 split around the holidays, after three years of dating. Johnson has moved out of the Baltimore home they shared to return to Los Angeles.

“Johnson is very interested in pursuing her career. Michael is tied up with swimming,” Keith Lewis, executive director for Miss California USA, told us, confirming the split. “Over the course of time, Baltimore didn’t hold the same opportunity that LA did.”

Johnson was already dating Phelps when she won her pageant title, and Phelps joined her at the 2011 Miss California USA pageant last January, where she passed her crown on to Alyssa Campanella, the current Miss USA.

“She introduced him as the man in her life,” Lewis told us. Shortly after, Johnson moved to Baltimore to be with Phelps, now in training for the 2012 London Olympics.

Despite printed chatter of liaisons with other women — including reality-TV starlet Brittny Gastineau — Johnson insists that Phelps was faithful. “Nicole would not have made a move to Baltimore had she not thought they were in a position where they were looking toward the future,” Lewis added.

But the pair split just before Christmas, and Phelps headed to New York to party with friends on New Year’s Eve at Chelsea hot spot Avenue. Meanwhile, Johnson went back to LA. She’s currently auditioning for hosting and other entertainment gigs. “She’s feeling great and really glad to be home,” said Lewis, who added she’s already going on dates with other men.

Johnson said through a rep: “The one thing we have in common is that neither of us have ever talked to the media about our personal life. I wish him all the luck at the Olympics. Go USA!” A rep for Phelps didn’t get back to us.