Mafia Wars is a defunct freemium multiplayer social network game created by Zynga. Players assume the roles of gangsters while building their own Mafia-type organization. The players fight and "rob" other players online - completing jobs, missions, and operations to gain rewards and strength in an endless game.

Mafia Wars won the 2009 Webby Award People's Voice Winner in the Games category.

A sequel, Mafia Wars 2, was released in October 2011 and was shut down on December 30, 2012. On April 5, 2016, it was announced via Zynga's forums that Mafia Wars would close down on June 6, 2016. Players were informed of this via an in-game message. The game was taken offline shortly past midnight PDT on June 7, 2016. The game was relaunched on mobile in April 2017 for selected markets, featuring revamped mechanics. In July 2017, Zynga announced that all future work on the game was cancelled and the game was discontinued.

Mafia Wars is set with a choice of playing in New York City or Chicago with the option for players to travel to other locations, such as London, South Africa, and Mexico. Other locations were formerly available.

The game revolved around fighting and robbing other players, doing jobs, missions, and operations to earn cash, building parts, weapons, attack and defence fighting skills, and experience, to establish and advance one's criminal empire. Players created mafias by recruiting other players or winning or buying artificial members (Hired Guns). Other players could be added to one's mafia through Facebook.

Gameplay was limited by three measurements: Energy, used for completing jobs, as well as Stamina and Health, which were used for fighting or robbing other players. The first two meters slowly recharged over time or filled up when experience was gained from levelling up. Fighting other players sometimes resulted in the theft of cash, the "killing" of the player attacked, or random gifts of loot (weapons, building parts, or consumable job supplies). Outcomes of an attack or attempt to rob were calculated by a formula that took into account the respective player's fighting skill, the number and quality of five kinds of weapons (weapons, armoury, vehicles, animals and henchmen), and a randomizing factor. When a player won an attack, they did damage to the victim's Health and suffered a loss of Health to their character.

Mafia Wars was released as an iOS app on April 8, 2009. Mafia Wars was available on Facebook, MySpace, Bebo, Yahoo!, and as a Google Chrome app.

On Facebook, Mafia Wars had up to 45.5 million monthly accounts created.