Albus Dumbledore (HARRY POTTER)

Harry Potter author JK Rowling has revealed that one of her characters, Hogwarts school headmaster Albus Dumbledore, is gay.

She made her revelation to a packed house in New York's Carnegie Hall on Friday, as part of her US book tour.

She took audience questions and was asked if Dumbledore found "true love".

"Dumbledore is gay," she said, adding he was smitten with rival Gellert Grindelwald, who he beat in a battle between good and bad wizards long ago.

The audience gasped, then applauded. "I would have told you earlier if I knew it would make you so happy," she said.

"Falling in love can blind us to an extent," she added, saying Dumbledore was "horribly, terribly let down" and his love for Grindelwald was his "great tragedy".

"Oh, my god," Rowling, 42, concluded with a laugh, "the fan fiction".

Rowling said her books are a "prolonged argument for tolerance"

Fan sites have long speculated on Dumbledore's sexuality as he was known for having a mysterious, troubled past.

Rowling told the audience that while working on the planned sixth Potter film, Harry Potter and the Half-Blood Prince, she saw the script carried a reference to a girl who was once of interest to Dumbledore.

She said she ensured director David Yates was made aware of the truth about her character