Brigitte Nielsen -- the OG "Red Sonja" -- isn't calling for director Bryan Singer's head just yet, but says she absolutely will ... IF troubling new pedophilia allegations turn out to be true.
We got Brigitte -- who costarred alongside Arnold Schwarzenegger in the '85 action flick -- leaving Craig's in WeHo, and asked what she made of Singer still directing the reboot ... after The Atlantic published a bombshell report in which 4 men claimed Singer had either molested them years ago when they were minors.
The Danish-born actress wasn't fully aware of the scandal, but invoked the #MeToo movement and told us if Singer turns out to be guilty -- he's gotta get the boot.
Sonja went so far as to say she'd cut him herself, if the studio didn't do it.
Little background: the fictional Sonja character is a victim of sexual assault, a fact that helped fuel the outrage over Singer possibly directing the film.
Singer is denying all the allegations and calls the Atlantic article a "homophobic smear piece." He has not been charged with any crime. For now, Brigitte is willing to reserve judgment until Singer is proven guilty of anything.
Millennium Media, which is making the film, and producer Avi Lerner are taking a similar approach ... saying Singer will not be fired based on mere allegations.