Giuseppe "Joe" Aiello (Italian pronunciation: [dʒuˈzɛppe aˈjɛllo]; September 27, 1890 – October 23, 1930) was a Sicilian bootlegger and organized crime leader in Chicago during the Prohibition era. He was best known for his long and bloody feud with Chicago Outfit boss Al Capone.

Aiello masterminded several unsuccessful attempts to assassinate Capone, and fought against his former business partner Antonio Lombardo, a Capone ally, for control of the Chicago branch of the Unione Siciliana benevolent society. Aiello and his ally Bugs Moran are believed to have arranged the murder of Lombardo, which directly led Capone to organize the St. Valentine's Day Massacre in retaliation.

Despite being forced to flee Chicago multiple times throughout the gang war, Aiello eventually took control of the Unione Siciliana in 1929, and ranked seventh among the Chicago Crime Commission's list of top "public enemies". Aiello was killed after Capone gunmen ambushed him as he exited a Chicago apartment building where he had been hiding out, shooting him 59 times. After his death, the Chicago Tribune described Aiello as "the toughest gangster in Chicago, and one of the toughest in the country".

Aiello was born on September 27, 1890, in Bagheria, Sicily, to father Carlo Sr. Aiello was part of a large and impoverished family of at least nine other brothers and many cousins. His mother died when he was a child. In July 1907, at the age of 17, Aiello immigrated to the United States to join family members already residing there. After arriving in New York City by boat, he worked a series of menial jobs in Buffalo and Utica, New York, before connecting with his father, brothers and cousins in Chicago. The family set up several businesses in both New York and Chicago, including the financially successful Aiello Brothers Bakery, and they become importers of such groceries as olive oil, cheeses and sugar.

Aiello was the co-owner of a cheese importing business with a fellow Sicilian, Antonio "Tony the Scourge" Lombardo, an ally of organized crime figure Al Capone. Aiello was president of the company, which was called Antonio Lombardo & Co., and Capone was said to have lent both men $100,000 to start the enterprise. With the enactment of Prohibition and the start of bootlegging, the sugar import business brought Aiello into contact with organized crime, along with his brothers Dominick, Antonio, Andrew and Carlo. In Chicago they made a small fortune selling sugar and other home-cooked alcohol components to the Genna crime family, and Aiello earned enough money to buy a three-story mansion in Rogers Park. However, he craved recognition and prestige in addition to money, something he was gaining as he was becoming known as the top organized crime boss of Chicago. When the Genna family lost power in Chicago following gang wars, the Aiellos believed themselves the successors of their territory.

In November 1925 Lombardo was named head of the Unione Siciliana, a Sicilian-American benevolent society that had been corrupted by gangsters. An infuriated Aiello, who had wanted the position himself, believed Capone was responsible for Lombardo's ascension and he resented the non-Sicilian's attempts to manipulate affairs within the Unione. Aiello severed all personal and business ties with Lombardo and entered into a feud with him and Capone, essentially ending a Chicago gang peace treaty that had been in force since the 1926 murder of Capone rival Hymie Weiss. Aiello allied himself with several other Capone enemies, including Dean O'Banion, and the trio of Billy Skidmore, Barney Bertsche and Jack Zuta, who ran vice and gambling houses together, although they became less receptive to Aiello after Capone personally approached and threatened Skidmore. While newspapers falsely reported that Aiello had also entered into an active alliance with George "Bugs" Moran and his North Side Gang at this time, Moran in fact pledged no specific support to Aiello until later, and instead privately supported Aiello from the sidelines without actively participating.

Aiello plotted to eliminate both Lombardo and Capone, and starting in the spring of 1927 made several attempts to assassinate Capone. On one occasion he offered money to the chef of Joseph "Diamond Joe" Esposito's Bella Napoli Café, Capone's favorite restaurant, to put prussic acid in Capone's and Lombardo's soup; reports indicated he offered between $10,000 and $35,000. Instead, the chef exposed the plot to Capone, who responded by dispatching men to destroy one of Aiello's stores on West Division Street with machine-gun fire. More than 200 bullets were fired into the Aiello Brothers Bakery on May 28, 1927, wounding Joe's brother Antonio. During the summer and autumn of 1927 a number of hitmen Aiello hired to kill Capone were themselves slain. Among them were Anthony Russo and Vincent Spicuzza, each of whom had been offered $25,000 by Aiello to kill Capone and Lombardo. Aiello eventually offered a $50,000 reward to anyone who eliminated Capone. At least 10 gunmen tried to collect on Aiello's bounty, but ended up dead. Capone ally Ralph Sheldon attempted to kill both Capone and Lombardo for Aiello's reward, but Capone henchman Frank Nitti's intelligence network learned of the transaction and had Sheldon shot in front of a West Side hotel, although he didn't die.

In November 1927 Aiello organized machine-gun ambushes across from Lombardo's home and a cigar store frequented by Capone, but those plans were foiled after an anonymous tip led police to raid several addresses and arrest Milwaukee gunman Angelo La Mantio and four other Aiello gunmen. After the police discovered receipts for the apartments in La Mantio's pockets, he confessed that Aiello had hired him to kill Capone and Lombardo, leading the police to arrest Aiello himself and bring him to the South Clark Street police station. Upon learning of the arrest, Capone dispatched nearly two dozen gunmen to stand guard outside the station and await Aiello's release. The men made no attempt to conceal their purpose there, and reporters and photographers rushed to the scene to observe Aiello's expected murder. Capone gunmen Frank Perry, Sam Marcus and Louis "Little New York" Campagna were arrested as they tried to enter the front of the station and placed in the cell next to Aiello, who Campagna told, "You're dead, friend, dead. You won't get up to the end of the street still walking". Aiello pleaded for mercy and promised to sell his possessions and leave Chicago with his family if they let him go, but Campagna refused the request. When released, Aiello was given a police escort out of the station to safety. He later failed to make a court appearance after his attorney claimed he suffered a nervous breakdown. Aiello disappeared with some family members to Trenton, New Jersey, from whence he continued his campaign against Capone and Lombardo.