Transgender actress Alexis Arquette sat down for an interview with Frontiers LA, and she claims that she slept with Jared Leto -- before her gender reassignment!

Alexis, who was born Robert, made the transition from male to female 13 years ago, and when asked to spill a secret, she said, "I had sex with Jared Leto back when I was presenting as a male. And, yes, it's not only massive -- it's like a Praetorian Guard's helmet." Double the woah!

Leto won an Oscar last year for his role as a transgender character Dallas Buyers Club, and though he's been with all sorts of beautiful women over the years (including Cameron Diaz, who he was with from 1999 to 2003), but this is the first we've heard of him getting down with a dude!

Neither Jared nor his rep have commented on the allegations...