Antonio Margarito Montiel (born on March 18, 1978 in Torrance, California) is a Mexican-American professional boxer. He is a former World Boxing Association, International Boxing Federation, and World Boxing Organization Welterweight champion. Margarito's reputation was tarnished by an incident in which his corner is alleged to have tampered with his hand wraps prior to his bout with Shane Mosley, which were found by the CSAC to contain sulfur and calcium which, when combined with oxygen, forms "Plaster of Paris". He's trained by former IBF Super Featherweight Champion Roberto García. Antonio also manages IBF Lightweight Champion Miguel Vazquez. Margarito resides in Tijuana, Mexico with his wife Michelle Margarito.

Margarito compiled a record of 18-3 in his relatively brief amateur career, indicating that he may have turned pro quickly due to financial concerns.

Margarito made his debut at the age of 15, beating Jose Trujillo in Tijuana by decision. On April 25, he achieved his first knockout, defeating Victor Angulo in the second round. On October 17 he suffered his first defeat, a six round decision to Victor Lozoya. Over the next six bouts he went 4-2. Following that he went 28-2-1, with notable wins over Alfred Ankamah, Juan Soberanes, future world Middleweight Champion Sergio Gabriel Martinez, Buck Smith, David Kamau and Frankie Randall, a former World Jr. welterweight champion who became the first man to beat Julio César Chávez in 91 fights.