During 1989 Sontag was the President of PEN American Center, the main U.S. branch of the International PEN writers' organization. After Iranian leader Ayatollah Khomeini issued a fatwa death sentence against writer Salman Rushdie for blasphemy after the publication of his novel The Satanic Verses that year, Sontag's uncompromising support of Rushdie was crucial in rallying American writers to his cause.
Sontag had a close romantic relationship with photographer Annie Leibovitz. They met in 1989, when both had already established notability in their careers. Leibovitz has suggested that Sontag mentored her and constructively criticized her work. During Sontag's lifetime, neither woman publicly disclosed whether the relationship was a friendship or romantic in nature. Newsweek in 2006 made reference to Leibovitz's decade-plus relationship with Sontag, stating, "The two first met in the late '80s, when Leibovitz photographed her for a book jacket. They never lived together, though they each had an apartment within view of the other's." Leibovitz, when interviewed for her 2006 book A Photographer's Life: 1990-2005, said the book told a number of stories, and that "with Susan, it was a love story." While The New York Times in 2009 referred to Sontag as Leibovitz's "companion," Leibovitz wrote in A Photographer's Life that, "Words like 'companion' and 'partner' were not in our vocabulary. We were two people who helped each other through our lives. The closest word is still 'friend.'" That same year, Leibovitz said the descriptor "lover" was accurate. She later reiterated, "Call us 'lovers.' I like 'lovers.' You know, 'lovers' sounds romantic. I mean, I want to be perfectly clear. I love Susan."