Leonardo DiCaprio -- I Do an AMAZING Jack Nicholson

Here's Jack Nicholson ... or is it Leonardo DiCaprio ... or is it Jack Nicholson??? WE HAVE NO IDEA!!!

Actually, yes we do. It's Leonardo DiCaprio doing one of the best Jack Nicholson impressions we've ever seen.

Leo whipped out the impersonation on some Japanese TV show ... doing his "Nicholson" eyebrows ... and he looks exactly like Jack in "Chinatown."

Sadly, Leo doesn't do his Jack voice ... but with Nicholson eyebrows this impressive, he doesn't really need it.