Will Ferrell -- What's Up with the Mustache?

Will Ferrell threw on his finest Ireland soccer jersey and hit up an art show in Miami Beach today -- sportin' some facial hair that begs the question ... IS THAT MUSTACHE FOR "ANCHORMAN 2?"

Ferrell was hangin' out at something called Art Basel -- which hails itself as a "premier art show for modern and contemporary works."

Owen Wilson and Diddy were also spotted at the event ... sans mustaches.

You stay classy.