Olympic hero Michael Phelps has split with his longtime girlfriend Nicole Johnson, a former Miss California. The champion swimmer and the brunette had been dating on and off for several years, and she traveled with him in July to the FINA World Championships in Shanghai. Sources say the couple broke up a few weeks ago, and Phelps is telling friends he’s single. Baltimore-born Phelps spent New Year’s Eve partying with six guy friends and six girls at Chelsea hot spot Avenue. Meanwhile Johnson, according to her Twitter feed, spent the night in LA with friends. A rep for Phelps, in training for the 2012 Olympics, didn’t get back to us.