Metal Gear Solid 2: Sons of Liberty (commonly abbreviated as MGS2) is a stealth game directed by Hideo Kojima, developed by Konami Computer Entertainment Japan and published by Konami for the PlayStation 2 in 2001. Chronologically, it is the sixth game in the Metal Gear series and a direct sequel to Metal Gear Solid.

The story revolves around a massive offshore clean-up facility that has been seized by terrorists calling themselves the "Sons of Liberty." They demand a massive ransom in exchange for the life of the President of the United States, and threaten to destroy the facility and create a cataclysmic environmental disaster if their demands are not met. The motives and identities of many of the antagonists and allies change rapidly, as the heroes discover a world-shaking conspiracy constructed by a powerful organization known as the Patriots, also referred to in the game as the La-Li-Lu-Le-Lo.

In spite of controversy concerning the character of Raiden, the game was well-received publicly and critically, shipping over 7 million copies worldwide and scoring an average of 95% in Game Rankings' aggregate. The unprecedented length, the complexity and deeply philosophical nature of its storyline (which explores the themes of memes, reality, conspiracy, AI, censorship, human nature, among others), divided both game reviewers and the public.

Its release was followed by an expanded edition, Metal Gear Solid 2: Substance for PlayStation 2, Xbox and Windows. Metal Gear Solid 3: Snake Eater, a prequel to the entire Metal Gear series, followed in 2004. A direct sequel to Sons of Liberty, titled Metal Gear Solid 4: Guns of the Patriots, is currently in development for release on the PlayStation 3 console.