Mariah Carey -- I'm the New Kate Upton in Game of War

Mariah Carey will be the new face and new set of ample boobs for the ridiculously successful "Game of War: Fire Age"... TMZ has learned.

Sources familiar with the situation tell TMZ ... producers of the mobile game have inked a 7 figure deal with Mariah, who replaces Kate Upton, in which the singer will shoot a 30 second commercial. We're told the shoot will last 2 days and the guy in charge is the director for "Terminator Genisys."

Mariah will do several other promotional shoots for the game, but the main thing is the commercial.

'Game of War' is a phenomenon, raking in $1 million a day.

Mariah is a bigger star than Kate Upton for sure, but it's something of a left turn. We're told one of the big selling points is that Mariah's music will be part of the spot.