Wladimir Klitschko -- Childbirth Is Tougher Than Any Fighter ... 'Hayden Is a Hero'

Tyson ... Ali ... Rocky -- they've all got NOTHING on Hayden Panettiere ... or any other woman who's ever had to give birth ... so says Hayden's boxing superstar baby daddy Wladimir Klitschko.

Wlad says Hayden's pain tolerance must be through the roof in order for her to have pushed out their giant baby 2 months ago ... saying he now believes women are WAY tougher than any boxer.

"Every woman is a hero."

Hayden might be more of a hero than most ... considering their daughter Kaya was 7 lbs., 14 oz. and damn near 2 feet tall. Hayden's only 5 feet tall.

#Salute