Tim McGraw Walks Across Sunset Blvd Before Playing Whisky a Go Go

Sunset Boulevard has officially gone country -- all thanks to Tim McGraw -- who not only stunned fans as walked across the famous street ... but then rocked one of the town's most historic venues.

Tim and his band played a secret, invite-only show Monday night at Whisky a Go Go, but rather than sneak in the backdoor, he decided to greet fans in front of the joint ... walking from the London Hotel to the Whisky, and handing out plenty of high-fives in the process.

Once inside, Tim treated fans to a setlist that included everything from his old hits like "Something Like That," "Real Good Man," "The Cowboy in Me" and "Indian Outlaw" to some new songs off his forthcoming album "Standing Room Only."

BTW ... as if the strut across Sunset wasn't enough of a surprise, Tim also brought out his buddy Richard Marx and they sang "Don't Mean Nothing."

McGraw and his band jammed out for over an hour before ending the show with his latest single "Hey Whiskey" ... a fitting tune considering the name of the venue.