The Maggia is an international crime syndicate that is the world's most powerful organization dedicated to conventional crime (as opposed to subversive activities). Originating in southern Europe, the Maggia spread throughout non-Communist Europe and the Americas. Its presence in the United States first came to public attention in the 1890's, and the Maggia's widespread bootlegging of illegal liquor during the Prohibition Era has become legendary. Today the Maggia controls most of the illegal gambling, loan-sharking, and narcotics trade in the United States, as well as many legal gambling casinos in Atlantic City, New Jersey and Las Vegas, Nevada. It also has great influence within various labor unions, and controls politicians on every level of government. Especially in recent years, the Maggia has invested many of its illegal gains into legitimate businesses. However, the Maggia enforces a strict code of secrecy 'among its members, and does not hesitate to punish betrayals and failures with death. Often the Maggia marks one of its members for execution by having a Maggioso grasp the intended victim by the chin in the so-called "Maggia touch."

The Maggia is not a monolithic organization but is instead a coalition of many virtually independent groups known as "families." The leading members of each family are usually connected through familial or marital ties. The Maggia also has affiliations with other criminal groups such as the Morgan organization in New York City's Harlem. Several "families" are based in the New York City area. Three of these families have come to pre-eminence.

The Silvermane Family: Its leader is Silvio "Silvermane" Manfredi, one of the last of the legendary gangsters who came to notoriety during the 1920s and 1930s. This group conducts its activities along traditional Maggia lines, and is heavily involved with the narcotics trade. Silvermane uses unusual scientific means only for the personal goal of staving off his own death, and not for the family's activities. Although Silvermane has a son, Joseph, once known as Blackwing, his successor as family head will probably be his longtime rival, top Maggia lawyer Caesar "Big C" Cicero. It is unclear whether or not Silvermane has again assumed control of his organization since being turned into a cyborg.

The Hammerhead Family: Dominated by middle-aged Maggia traditionalists, this family first became notorious under unusual circumstances. Perhaps in imitation of the Nefaria family, its leader, known as the "Top Man," outfitted his family hit men with costumes and advanced weaponry. He then gained ownership of the Baxter Building through questionable means, thinking that doing so would somehow give him legal title to the technology of the building's famed occupants, the Fantastic Four. The Fantastic Four defeated and captured the "Top Man," his claims to owning the Baxter Building were dismissed by the courts, and the "Top Man" was reportedly assassinated by order of his own family. The family then sought a new leader who would direct operations along thoroughly traditional lines, and chose a newcomer known only as Hammerhead, an amnesia victim whose new ruthless persona had been shaped by his love for gangster films. Hammerhead uses methods from the Prohibition Era, including gang wars, although he will use advanced technology for personal ends, such as the exoskeleton that magnifies his strength.

The Nefaria Family: This group bears little resemblance to the rest of the Maggia. The late Italian nobleman, Count Luchino Nefaria, a scientific genius, was the world's most powerful Maggia leader until his initial defeat by the Avengers. Afterwards he moved his base of operations to the New York City area, and then imprisoned Washington, D.C. within an impenetrable force-dome and held it for ransom. After his defeat and capture, his daughter Giulietta, also known as Whitney Frost, succeeded him as family head and led an unsuccessful attempt to capture the advanced weaponry of Tony Stark. She was eventually succeeded by a costumed criminal, the Masked Marauder, who demanded complete control of New York City or else he would detonate a nuclear device there. After his capture, the family again apparently came under control of Whitney Frost, by then known as Madame Masque. Contrary to standard Maggia practice, the Nefaria family, principally consisting of men under 40, has employed futuristic weaponry and even robots (like the Dreadnoughts), as well as costumed super-powered agents (Unicorn, Whiplash, Gladiator, etc.), and has launched open attacks on society. Its leader is always known as "Big M." There are many other Maggia "families" in the United States and Europe which do not employ superhuman agents.

Various criminals have attempted to unify the American East Coast's independent criminal groups so as to compete with the Maggia domination of organized crime. The most successful of these has been the Kingpin.