Monzón was born on August 7, 1942, in San Javier, Santa Fe Province, Argentina, one of twelve children in a family that moved to the poor Barranquitas Oeste neighborhood of the city of Santa Fe while he was still young, according to his Wikipedia biography. He left school in the third grade and worked as a shoeshine boy, a paperboy and a milkman to help support his family, a hardscrabble upbringing that shaped the guarded, often volatile public figure he later became. Boxing offered one of the few visible routes out of that poverty in his neighborhood, and he began fighting as an amateur before turning professional in his early twenties.

Monzón made his professional debut on February 6, 1963, and spent most of the next seven years fighting largely unheralded opponents around Argentina and South America under trainer Amílcar Brusa, according to the New World Encyclopedia. He picked up the nickname “Escopeta,” or Shotgun, for his punching power, but his rise was not smooth: he lost three fights early in his career, all of which he later avenged, before embarking on what would become one of the longest unbeaten streaks in boxing history, reported at roughly 80 fights between 1964 and 1977. Purses for a largely unknown South American middleweight were modest, and it took a decade of fighting for him to earn a shot at a world title.

Monzón’s breakthrough came on November 7, 1970, in Rome, where he knocked out Italian favorite Nino Benvenuti in the 12th round with what Ring magazine’s own retrospective called “one of the most brutal knockout punches that the division had ever seen,” a result The Ring also named its fight of the year, according to Wikipedia. He reportedly earned only around $15,000 for that fight, a modest purse for a world title bout even by the standards of the day, according to a career retrospective from Reemus Boxing. The Benvenuti win turned Monzón from a little known challenger into an overnight star in Argentina and, soon after, in Europe, where he would fight almost exclusively for the rest of his championship reign.

Over the next seven years Monzón defended his middleweight title 14 times against 11 different opponents, including two wins each over Emile Griffith and Rodrigo Valdez, plus victories over José Nápoles, Bennie Briscoe and Tony Mundine, a title defense record that stood for years, according to Boxing 24/7’s retrospective on his career. The WBC stripped him of its portion of the title in 1975 for failing to face a mandatory challenger, but he unified the championship again by beating Valdez on June 26, 1976. He retired undefeated as champion on August 29, 1977, finishing with a professional record of 87 wins, 59 by knockout, against 3 losses, 9 draws and 1 no contest across 100 bouts, a tally confirmed by Ring magazine’s career retrospective.

Monzón shared The Ring magazine’s 1972 Fighter of the Year award with Muhammad Ali and was voted the best middleweight titleholder of the previous 50 years by the same publication in 2011, according to his Wikipedia biography. His only fight in the United States, a June 30, 1975 title defense against Tony Licata at Madison Square Garden, earned him a Sports Illustrated cover under the headline “Monzon The Magnificent,” coverage detailed by ESPN’s account of the fight. In 1990 he became the first Argentine boxer inducted into the International Boxing Hall of Fame, a distinction that has kept his name at the center of debates over the greatest middleweight in the sport’s history alongside Sugar Ray Robinson and Marvin Hagler, a comparison Boxing 24/7 lays out directly.

Monzón’s career predates the modern athlete endorsement industry, and there is no detailed public record of formal sponsorship contracts comparable to what a champion of his stature would sign today. His outside income instead came from fight purses, a run of film and television appearances, and public appearances tied to his celebrity status in Argentina, a pattern consistent with the boxing economics of the 1970s described across his Wikipedia biography and the Legends of Boxing profile of his career.

Public reporting on Monzón’s business life outside boxing is thin compared with the detail available on his ring career, but what does exist is not flattering: a career retrospective from Reemus Boxing states plainly that he lost “considerable money in failed business ventures” even as he continued to live a wealthy, high profile lifestyle through his television and film appearances. No public record identifies the specific companies or investments involved, which is itself notable given how closely his ring earnings, films and personal life were covered by the Argentine press of the period.

There is no reliable public record detailing specific real estate, vehicles or other major assets Monzón owned at the height of his career or at the time of his death. The closest documented evidence of his financial trajectory is the account from Reemus Boxing of money lost in failed business ventures despite a lavish lifestyle, which points to instability in his finances but does not identify or value any specific holdings. In the absence of a probate record, an estate accounting or contemporaneous reporting naming particular properties, HMW is not able to attach a sourced figure to any individual asset.