Hollywood kingpin Barry Diller has, for the first time, shared his thoughts on the decades of speculation about his sexuality and his marriage to fashion designer Diane von Furstenberg in an excerpt of his upcoming memoir that appeared in New York Magazine on Tuesday.

The former Paramount and Fox boss said that while there have been a “good many men in my life, there has only ever been one woman” — von Furstenberg, whom he met shortly after getting the top job at Paramount in the mid-1970s. The pair were together for years in the ’70s, before breaking up and later marrying in 2001.

Diller, in the endearing and revealing excerpt, said he had been “realistic” that “everyone knows” in the entertainment world that he is attracted to men, but that he “never wanted to make any declarations.” But long-running rumors that his relationship with von Furstenberg is merely an arrangement or friendship are untrue,...