Lenny Dykstra: If Mickey Rourke Wants a Fight, LET'S FIGHT ALREADY!

Lenny Dykstra says he's done trading insults with Mickey Rourke -- AND NOW HE WANTS TO FIGHT!!!

The ex-MLB star says he saw the recent video of Mickey threatening to beat up Lenny on sight -- and says he's sick and tired of the talk ... it's time to put up or shut up.

"You know what dude ... we need to f***ing get it on! Mano y f***ing Mano. In front of the f***ing world so I can f***ing embarrass your f***ing ass."

Dykstra lays out THREE reasons why Mickey needs to agree to a REAL DEAL boxing match -- one of which is, "What's the worst thing, you can't get any f***ing uglier after I f***ing rearrange your f***ing face mother f***er."

We'll reach out to Mickey for his reaction ... stay tuned.