During his decades as a media mogul, Barry Diller has held an array of powerful titles, serving as chairman and chief executive of Fox, Paramount Pictures and, most recently, IAC. The positions have made Mr. Diller a boldfaced name and a billionaire.

Now, however, Mr. Diller, 83, has embraced a new role: that of an openly gay man.

The announcement came on Tuesday morning via an excerpt from a forthcoming memoir, “Who Knew,” published in New York magazine, which recounts his life, including his relationship with the designer and socialite Diane von Furstenberg, whom he has been married to since 2001.

“While there have been a good many men in my life, there has only ever been one woman,” Mr. Diller writes, calling his relationship with Ms. von Furstenberg “the miracle of my life,” despite it causing “confusion and lots of speculation.”

At the same time, Mr. Diller also writes of a quiet suffering he felt by hiding his sexuality, and a fear of exposure that “stunted any chance of my having a fulfilling personal life.”

He added that he “had discovered I could separate myself from anything painful or terrifying by just locking it away, putting it into a distant box and having to deal with it hopefully never.”

In the memoir, Mr. Diller says his early sexual experiences with men came during his teenage years “cruising in West Hollywood, darting in and out of side doors of bars along Melrose Avenue.”