Hayden Panettiere Publicly Comes Out as Bisexual

Hayden Panettiere's finally letting the cat outta' the closet -- proudly revealing for the very first time ... she's bisexual!

The actress made the emotional confession while promoting her new memoir, "This Is Me: A Reckoning," dropping May 19 ... declaring in empowerment, "I'm comfortable to confidently say that, yes, I am bisexual. I said it!"

Hayden told Us Weekly the book dives into how she started dating women at a young age -- admitting she felt more drawn to them than men ... but back then, she says the pressure to stay perfect in Hollywood kept her quiet.

The star also recalled having zero privacy with paparazzi constantly around ... so while she explored her sexuality behind closed doors, she never fully allowed herself to emotionally dive in. Part of the fear? Falling in love with a woman and feeling forced to hide it!