Portal 2 is a 2011 puzzle-platform video game developed by Valve for Windows, Mac OS X, Linux, PlayStation 3, and Xbox 360. The digital PC version is distributed online by Valve's Steam service, while all retail editions were distributed by Electronic Arts. A port for the Nintendo Switch was included as part of Portal: Companion Collection.

Like the original Portal (2007), players solve puzzles by placing portals and teleporting between them. Portal 2 adds features including tractor beams, lasers, light bridges, and paint-like gels that alter player movement or allow portals to be placed on any surface. In the single-player campaign, players control Chell, who navigates the dilapidated Aperture Science Enrichment Center during its reconstruction by the supercomputer GLaDOS (Ellen McLain); new characters include robot Wheatley (Stephen Merchant) and Aperture founder Cave Johnson (J. K. Simmons). In the new cooperative mode, players solve puzzles together as robots Atlas and P-Body (both voiced by Dee Bradley Baker). Jonathan Coulton and the National produced songs for the game.

Valve announced Portal 2 in March 2010, and promoted it with alternate reality games including the Potato Sack, a collaboration with several independent game developers. After release, Valve released downloadable content and a simplified map editor to allow players to create and share levels.

Portal 2 received critical acclaim for its gameplay, balanced learning curve, pacing, dark humor, writing, and acting. Like its predecessor, it has been described as one of the greatest video games ever made by numerous publications and critics.