The year 2003 is the fifth year in the history of King of the Cage, a mixed martial arts promotion based in the United States. In 2003 King of the Cage held 11 events, KOTC 21: Invasion.
KOTC 21: Invasion was an event held on February 21, 2003, at the Santa Ana Star Hotel & Casino in Albuquerque, New Mexico, United States.
KOTC 22: Steel Warrior was an event held on March 23, 2003, at the Soboba Casino in San Jacinto, California, United States.
KOTC 23: Sin City was an event held on May 16, 2003, at the Orleans Hotel Casino in Las Vegas, Nevada, United States.
KOTC 24: Mayhem was an event held on June 14, 2003, in Albuquerque, New Mexico, United States.
KOTC 25: Flaming Fury was an event held on June 29, 2003, at the Soboba Casino in San Jacinto, California, United States.
KOTC 26: Gladiator Challenge was an event held on August 3, 2003, at the Sky City Casino in Acoma, New Mexico, United States.
KOTC 27: Aftermath was an event held on August 10, 2003, at the Saboba Casino in San Jacinto, California, United States.
KOTC 28: More Punishment was an event held on August 16, 2003, in Reno, Nevada, United States.
KOTC 29: Renegades was an event held on September 5, 2003, at the Soboba Casino in San Jacinto, California, United States.
KOTC 30: The Pinnacle was an event held on November 12, 2003, at the Pala Casino Spa Resort in Pala, California, United States.
KOTC 31: King of the Cage 31 was an event held on December 6, 2003, at the Soboba Casino in San Jacinto, California, United States.