Jay Leno -- I'm Done With Television ... FOR GOOD

Don't expect Jay Leno to hijack "The Tonight Show" back from Jimmy Fallon ... because the ex late-night host swears he's done with TV ... FOREVER.

Jay was in West Palm Beach Florida -- but not to start his retirement. Leno was there to perform stand-up comedy just two days after his exit from "The Tonight Show."

Jay's answer may come as a surprise ... especially since he left the show in 2010 ... then famously wrangled it back from Conan O'Brien.