Born on September 12, 1957 in La Romana, the largest city of Dominican Republic, Eleoncio Mercedes was a world champion boxer in the Flyweight division.
Most of Mercedes' boxing career was spent in the United States and Mexico. He debuted as a professional boxer on July 2 of 1978 in a fight against Darryl Jones in which he won. His first taste of defeat was in a fight against Joey Olivo in Las Vegas. It was Mercedes' third bout as a professional boxer. It was in 1979 where his first eleven fights were done in Mexico. During that span of his boxing career, he garnered 6-3-2 record in various Mexican places such as Mexico City, Reynosa, and Monterrey. He also lost to Candido Tellez and Juan Diaz but eventually beat Guty Espadas, a former world boxing champion by a knockout
In 1982, Mercedes had his first boxing fight in his home country through a rematch with Diaz. The fight was held in Santo Domingo and ended with Mercedes winning the bout by decision in twelve rounds. Until that moment, his record was 10-6-2 – 10 wins, six losses, and two draws.
In a surprising decision, the World Boxing Conference (WBC) announced that they are giving Mercedes the chance to be a world champion. On November 6, 1982, he fought two time world champion Freddie Castillo in Los Angeles. Surprisingly, Mercedes won the fight and brought home the World Flyweight Champion, a title that gave pride to Dominican flag. Mercedes defended his title for the first time against Charlie Magri. During the seventh round of the fight he suffered a cut and eventually lost his title to Magri. After that, he continued his boxing career but was only able to win some.
On December 22, 1985, at the aged of 28, Mercedes was killed by a police officer in unclear circumstances. He was shot because he was allegedly pulling out a gun at the police officer.