Batman's longtime sidekick Catwoman is set to 'come out' as a bisexual in a new comic.

The feline-esque femme fatale, who has been played on screen by Julie Newmar, Anne Hathaway, Halle Berry and Michelle Pfeiffer, will kiss a female character, called Eiko, in a new comic strip created by Genevieve Valentine.

In a blog post, the comic book artist says, "For me, this wasn't a revelation so much as a confirmation."

But it might upset many Batman fans, who felt sure Selina Kyle's alter-ego was destined to become the Caped Crusader's girlfriend.

Valentine adds, "I don't want to spoil what can't yet be spoiled, please be assured that Selina's longstanding connection to Batman has not been forgotten; that is not how bisexuality (or humanity) works. Selina doesn't care easily, but when she does care it strikes deep, and there will be plenty of that coming up."