Sean Penn, 51, has a new girlfriend, Shannon Costello, 26. They began dating soon after his previous girlfriend, Scarlett Johansson, 26, split from Penn in June. He and Shannon, who was first misidentified as Stacey Koplin, went public in July and were seen together on the beach in Malibu during the Fourth of July weekend, and later spotted dining in Miami. Penn met Costello back in 2009, when they were working on the actor’s J/P Haitian Relief Organization together. Costello also produces films, and will work alongside Brian Grazer on Ron Howard‘s new film, Under The Banner of Heaven, which is still in the development phase. Meanwhile, Scarlett Johansson, 26, is rumored to be dating 33-year-old The Hangover star, Justin Bartha.