The Oscar-winner teed off on movie critics during an epic rant on Conan O'Brien's podcast ... ripping them for some of the responses he's gotten over his long career in Hollywood.

One movie sticks out to Tom and Conan ... his 1996 flick "That Thing You Do!" It was Tom's debut as a screenwriter and director and it got bad reviews at first, but now it's considered a cult classic and Tom says one critic who ripped the film is now doing a 180.

Tom tells Conan and the gang ... "Let me tell you something about these c***suckers who write about movies. Can I say that?"

Conan laughs, makes a joke and Tom continues ... "Somebody who wrote about it is, 'Tom Hanks has to stop hanging around with veterans of TV, because this is just like shot on TV and it's not much of anything.'"

Tom says that same critic is now changing their tune ... "That same person then wrote about the cult classic 'That Thing You Do!' Same exact person. They said, 'All you need is 20 years between now and then, and it ends up speaking some words.'"

For Tom, it sounds like his issue with movie reviews is that they're too black and white ... and he even makes a joke about getting a gun when a review comes in.