The MGM along with half of the other major hotels on the Strip (Bellagio, Circus Circus, CityCenter [if it ever opens], Excalibur, Luxor, Mandalay Bay, Mirage, Monte Carlo, NYNY, and Treasure Island) are owned by MGM-Mirage. Any partnership Marriott had with MGM was probably done before MGM Grand merged with Mirage Resorts in 2000 and as such would more than likely no longer exist. The other half of the Strip (Bally's, Caesar's Palace, Flamingo, Harrah's, Imperial Palace, Paris, and Rio [although not on the Strip]) is owned by Harrah's Corporation. (My UNLV education finally does me some good )