Metal Gear Solid 2: Sons of Liberty is a 2001 action-adventure stealth video game developed by Konami Computer Entertainment Japan and published by Konami for the PlayStation 2. Originally released on November 13, 2001, it is the fourth Metal Gear game produced by Hideo Kojima, the seventh overall game in the series and is a sequel to Metal Gear Solid (1998). An expanded edition, titled Metal Gear Solid 2: Substance, was released the following year for Xbox and Windows in addition to the PlayStation 2. A remastered version of the game, Metal Gear Solid 2: Sons of Liberty - HD Edition, was later included in the Metal Gear Solid HD Collection for the PlayStation 3, Xbox 360, and PlayStation Vita. The HD Edition of the game was included in the Metal Gear Solid: Master Collection Vol. 1 compilation for Nintendo Switch, PlayStation 4, PlayStation 5, Windows, and Xbox Series X/S, which was released on October 24, 2023.

Metal Gear are the mecha in the Metal Gear series. In the series, a Metal Gear is a bipedal nuclear weapons-equipped tank. The Metal Gears are typically autonomous nuclear launch platforms which the player must destroy to save the world and complete the game. Often, confronting the latest Metal Gear model is one of the final challenges of each game.