Motley Crue Retiring -- We're Done!!!

Shout at the devil ... for the last time ... TMZ has learned, Mötley Crüe is calling it quits after 33 years.

The iconic heavy metal band -- famous for hits like "Kickstart My Heart" and "Girls Girls Girls" -- just announced their retirement at a news conference inside Beacher's Madhouse Theater in Hollywood.

The stage was set with headstones, symbolizing each of the band's members -- singer Vince Neil, guitarists Nikki Sixx and Mick Mars, and drummer Tommy Lee.

But before they pull the plug, MC -- founded in 1981 by Nikki and Tommy -- said they'll be going on one last tour ... 72 tour dates.

We're told the tour will start very soon. Tickets go on sale tomorrow and Alice Cooper is set to open for them.

Oh yeah, and don't count on any Motley Crue reunion tour down the road -- we're told the band has collectively agreed NEVER to use the name "Motley Crue" ever again after this tour. This is really it.