Anthony Joseph Accardo (/əˈkɑːrdoʊ/; born Antonino Leonardo Accardo, Italian: [antoˈniːno leoˈnardo akˈkardo]; April 28, 1906 – May 22, 1992), also known as "Joe Batters" and "Big Tuna," was a mobster in the American Mafia. In a criminal career that spanned nearly eight decades, Accardo rose from small-time hoodlum to the position of day-to-day boss of the Chicago Outfit in 1947, to ultimately becoming the power behind the throne in the Outfit by 1972. Accardo moved the Outfit into new operations and territories, significantly increasing its power and wealth during his tenure as boss.

Tony Accardo was born on April 28, 1906, in Chicago's Near West Side, the second of six children of shoemaker Francesco Accardo and Maria Tilotta Accardo. One year before his birth, the Accardos had emigrated to the United States from Castelvetrano, in the Province of Trapani, Sicily, Italy. At age 14, Accardo left school and started loitering around neighborhood pool halls. He soon joined the Circus Cafe Gang, run by Claude Maddox and Tony Capezio, one of many street gangs in Chicago's impoverished neighborhoods. These gangs served as talent pools (similar to the concept of farm teams) for the city's adult criminal organizations. Jack "Machine Gun" McGurn, one of the toughest hitmen of crime boss Al Capone, recruited Accardo into his crew, along with longtime associate Tony Mazlack of Gary, Indiana.

During Prohibition, Accardo gained the nickname "Joe Batters" after using a baseball bat to murder three mobsters who had betrayed the Chicago Outfit. In 1939, Chicago newspapers dubbed Accardo "The Big Tuna" after he participated in a fishing expedition to Wedgeport, Nova Scotia, Canada, where he caught a giant 400-pound tuna and was photographed with his catch. In later years, Accardo boasted over federal wiretaps that he participated in the infamous 1929 St. Valentine's Day Massacre in which, allegedly, Capone gunmen murdered seven members of rival Bugs Moran's North Side Gang. He also claimed that he was one of the gunmen who murdered Brooklyn gang boss Frankie Yale, again by Capone's orders to settle a dispute. However, most experts believe Accardo had only peripheral connections, if any, with the St. Valentine's Day Massacre and none whatsoever with the Yale murder, which was most likely committed by Gus Winkler, Fred Burke and Louis Campagna. However, on October 11, 1926, Accardo may have participated in the assassination of Northside gang leader Hymie Weiss near the Holy Name Cathedral in Chicago.

In 1932, Capone was convicted of tax evasion and sent to prison for eleven years, and Frank "The Enforcer" Nitti became the new Outfit boss after serving his own eighteen-month sentence for the same offense. By this time, Accardo had established a solid record of making money for the organization, so Nitti allowed him to establish his own crew. Accardo was also named as the Outfit's head of enforcement. He soon developed a variety of profitable rackets, including gambling, loansharking, bookmaking, extortion and the distribution of untaxed alcohol and cigarettes. As with all caporegimes (captains), Accardo received five percent of the crew's earnings as a so-called "street tax." Accardo, in turn, paid a tax to Nitti. If a crew member refused to pay a street tax (or paid less than half of the amount owed), they would be killed. Accardo's crew included future Outfit heavyweights Gus "Gussie" Alex and Joseph "Joey Doves" Aiuppa.

In the 1940s, Accardo continued to gain power in the Outfit. As the decade progressed, senior members of the organization were investigated and charged with using the threat of strike action by the labor unions they controlled to extort millions of dollars from Hollywood studios. Nitti, who was claustrophobic and fearful of serving a second prison term, committed suicide in 1943. Paul "The Waiter" Ricca, who had been the de facto boss since Capone's imprisonment, took the role officially and named Accardo as underboss. Ricca and Accardo ran the Outfit for thirty years until Ricca's death in 1972. When Ricca subsequently received a ten-year prison sentence for his part in the Hollywood scandal, Accardo became acting boss. Three years later, when Ricca was barred from contact with mobsters as a condition for his parole, Accardo became boss of the Outfit; in practice, he shared power with Ricca, who remained in the background as a senior consultant.

Under Accardo's leadership in the late 1940s, the Outfit moved into slot and vending machines, counterfeiting cigarette and liquor tax stamps, and expanding narcotics smuggling. Accardo placed slot machines in gas stations, restaurants and bars throughout the Outfit's territory. Outside of Chicago, the Outfit expanded into Las Vegas and took influence over the city's gaming industry away from the Five Families of New York City. Accardo ensured all the legal Las Vegas casinos used his slot machines. In Kansas and Oklahoma, Accardo also took advantage of the official ban on alcohol sales to introduce bootlegged alcohol. The Outfit eventually dominated organized crime in most of the western United States. Accardo phased out some traditional activities, such as labor racketeering and extortion, to reduce the Outfit's exposure to legal prosecution. He also converted the Outfit's brothel business into call girl services. These changes resulted in a golden era of profitability and influence for the Outfit.

Accardo and Ricca emphasized keeping a low profile and let flashier figures, such as Sam Giancana, attract attention instead. For example, when professional wrestlers Lou Albano and Tony Altomare, wrestling as a Mafia-inspired tag team called "The Sicilians," came to Chicago in 1961, Accardo persuaded the men to drop the gimmick to avoid any mob-related publicity. By using tactics such as these, Accardo and Ricca were able to run the Outfit much longer than Capone. Ricca once said, "Accardo had more brains for breakfast than Capone had in a lifetime."

After 1957, Accardo turned down the official position as boss because of "heat" from the Internal Revenue Service (IRS). Accardo became the Outfit's consigliere, stepping away from the day-to-day running of the organization, but still retained considerable power and demanded ultimate respect. Despite officially being boss, Giancana still had to obtain the sanction of Accardo and Ricca on major business, including murders.