Hugh Hefner, 84, will marry Crystal Harris, 24, on June 18 at the Playboy Mansion, a representative told People magazine.
Harris has begun the search for a wedding dress and will pose in a pre-wedding Playboy spread, set to run shortly before the wedding in June.
Hefner engaged to Miss December 2009 on Christmas Eve by giving her a ring and not specifying that it was an engagement ring.
"He did it on purpose," Harris told The New Yorker. "All of a sudden it was everywhere. I had, like, fans in Sweden, Slovakia, Russia, everywhere."
After starring on the E! reality show, "The Girls Next Door" about the women who live in the Playboy mansion, Harris was still around after his other two 'girlfriends,' identical twins Karissa and Kristina Shannon had left.
"Yeah, it's just us," Harris told The New Yorker. "I mean, Hef has, like, had sex with a lot of people throughout the years, and that's not important to him anymore."
Hefner founded nude magazine Playboy in 1953. He is known for his wild parties and has often been seen in public surrounded by an entourage of Playmates. In recent years, he has lived in his mansion in Bel Air with several girlfriends, including "The Girls Next Door" stars Kendra Wilkinson and Holly Madison, who received their own spin-off shows. He has been linked to Harris since about 2009.
This will be the third marriage for Hefner. Hefner and Playmate Kimberley Conrad were married between 1989 and March of last year. They have two sons - Marston, 20, and Cooper, 19. Hefner divorced his first wife, Mildred Williams, in 1959 after 10 years of marriage. They have two children - Christie, 52, and David, 55.
According to The New Yorker, Harris is favoring a blush pink Romona Keveza gown for her walk down the aisle. Harris also revealed that the Playboy billionaire eats the same thing every day- Lipton's chicken noodle soup at 5 o'clock.