Arma 2 is a 2009 tactical shooter simulation video game developed and published by Bohemia Interactive for Microsoft Windows. It is the second main entry in the Arma series and the third installment in the series overall. The game is set in the fictional Eastern European country of Chernarus during a civil war between the Chernarussian government and communist revolutionaries, and follows escalating tensions when the United States Marine Corps is deployed to defeat the rebels.

Arma 2 was first released on 29 May 2009 in Germany, with further releases in Europe, North America, and other regions throughout June and July of that year. The game was positively received by critics who, like its predecessor Arma: Armed Assault, praised its realism and accuracy but criticized its difficulty and bugs. Arma 2 has sold 2.3 million copies as of February 2015. Arma 2 maintains a significant modding community and is well-known as the origin of DayZ, a survival game conversion that was later developed into its own standalone game in 2018 and contributed to the development of the battle royale game genre.

An expansion pack, Arma 2: Operation Arrowhead, was released in 2010. A free version of the game was released in June 2011 but was discontinued by 2014. The game's sequel, Arma 3, was released in 2013.

Arma 2 is a tactical shooter focused primarily on infantry combat, but significant vehicular and aerial combat elements are present. The player is able to command AI squad members which adds a real-time strategy element to the game. This is further enhanced by the high command system, which allows the player to command multiple squads using the map. Arma 2 is set primarily in the fictional Eastern European state of Chernarus (meaning "Black Rus"). The Chernarussian landscape is based heavily on the Czech Republic; the home country of the developer.

Arma 2, plus all expansions, features eleven distinct armed factions, each with their own vehicles and weapons. Caught in the middle are the Chernarussian and Takistani civilians. The factions included in Arma 2 are: USMC, Armed Forces of the Russian Federation, Chernarussian Defense Forces (CDF), Chernarussian Movement of the Red Star (ChDKZ), National Party (NAPA), and the citizens of Chernarus.

Arma 2 features around 80 realistically represented weapons with many variants including assault rifles, machine guns, and missile launchers, with realistically simulated ballistics.

There are around 130 vehicle variants, and any vehicle that exists in-game can be controlled by the player, including civilian cars, tractors and bicycles. Similarly, all aircraft encountered in the game can be flown by the player, with limited fuel and realistic weapon loadouts.

Arma 2 includes a mission editor which makes it possible to create user-made single player missions or campaigns and multiplayer missions through use of the in-game wizard. More complex missions can be enhanced with scripting commands. The syntax and interface have both been kept largely consistent with the Arma series, meaning that missions are ported across games.