Despite living in the Playboy Mansion with three of his girlfriends, it looks like Hugh Hefner truly has eyes for only one of them.

The 80-year-old founder and editor-in-chief of Playboy will reportedly be married to his No. 1 girlfriend, 27-year-old Holly Madison, before the end of the year, The New York Post reported on Monday.

"This is very secret, but the word is 'yes,'" an "insider" told The Post. "Hef has decided he will marry Holly, and he wants it for his show, The Girls Next Door. Hef thinks business all the time, and looks for a new hook, although he also does really love Holly."

While Madison is just one in a trio of big-breasted blond beauties living in the Playboy Mansion on E!'s The Girls Next Door reality series -- along with Bridget Marquardt and Kendra Wilkinson -- she is the one that sleeps in the same bed as Hefner.

"Hef sees that [Madison] is the most dedicated," the insider told The Post. "Kendra is never there, and [she and Madison] both hate each other, and Bridget is hanging on by being very friendly to Holly."

Madison moved into the Playboy Mansion in 2001 and over the years gradually became Hefner's No. 1 girlfriend.  During an April 2006 interview with Alan Colmes, Hefner stated that Madison was the true "love of his life." On episodes of The Girls Next Door, Madison has said she wants children with Hefner and often gives him hints.

The Girls Next Door premiered on E! in August 2005 and its third season is scheduled to begin airing in March.  Hefner, who has been married twice before, is keeping his wedding plans with Madison secret, according to The Post.