There are many casinos on the strip. Ownership is as follows:
Mandalay Resort Group (Circus Circus, Excalibur, Luxor) MGM/Mirage - Kirk Kerkorian (Bellagio, MGM, Monte Carlo, New York New York, Mirage, Treasure Island)
Some casinos are jointly owned. For example, Monte Carlo is 50% MRG and 50% MGM/Mirage.