Windosill is a 2009 puzzle video game by Vectorpark for Microsoft Windows, OS X, Linux, web browsers, and iOS. The player advances through eleven rooms through interacting with each level's environmental objects. It was developed by artist Patrick Smith, who taught himself to animate and program the game in Adobe Flash. He was inspired by a variety of painters and artists. The game was first released for Windows, OS X, and web browsers in 2009, and was later ported to the iPad in 2011 with several added features.

The game received "universal acclaim", according to video game review score aggregator Metacritic. Reviewers noted the game's especially short duration, memorability, art style, and emphasis on exploration over problem solving. Windosill has influenced games including Alto's Adventure, Blek, Donut County, and Monument Valley.