Kevin Spacey is vehemently denying Guy Pearce's allegation he was "targeted" by Spacey on a movie set back in the day ... and Kevin's taking shots at Guy too.

The "House of Cards" star just posted a video response to some recent comments Guy made about him ... telling Guy straight up he's not a victim.

Kevin says Guy's claim that Spacey targeted him when they were filming the 1997 movie "L.A. Confidential" is bogus ... and he's ripping Pearce for coming after him in the media.

Guy was on The Hollywood Reporter's "Awards Chatter" podcast and he got emotional recalling his experience with Kevin on the set of 'Confidential' ... claiming he was a victim of an "aggressive" Spacey.

Pearce said ... "I was sort of scared of Kevin because he's quite an aggressive man. He's extremely charming and brilliant at what he does -- really impressive, etc. He holds a room remarkably. But I was young and susceptible, and he targeted me, no question."

Kevin says he's not sure what Guy is referring to here and claims Pearce couldn't have been all that scared of him because he says Guy later visited him on a different movie set on the other side of the country.

Guy's previously claimed Kevin was a "handsy guy."

Spacey's been dogged by sexual harassment allegations for years now and he says he's been through hell and back ... vowing to defend himself in the face of Guy's claims.

It's a pretty intense response ... and Spacey tells Guy to grow up.