She was asked by one young fan whether Dumbledore finds "true love."
"Dumbledore is gay," the author responded to gasps and applause.
She then explained that Dumbledore was smitten with rival Gellert Grindelwald, whom he defeated long ago in a battle between good and bad wizards. "Falling in love can blind us to an extent," Rowling said of Dumbledore's feelings, adding that Dumbledore was "horribly, terribly let down."
Dumbledore's love, she observed, was his "great tragedy."
"Oh, my god," Rowling concluded with a laugh, "the fan fiction."