This chapter gives an overview of reflectarray antennas, covering from their historical development to the latest applications. A reflectarray antenna consists of an array of phase‐shifter cells, which are preadjusted to generate a collimated or shaped beam, when illuminated by an external source. The chapter describes different types of reflectarray cells, analysis and design techniques, as well as some realizations for bandwidth improvement, multifrequency operation, and beam scanning. Various selected applications of reflectarray antennas in radar, imaging, and communications are described. Some of them are already commercialized as automotive radars and imaging scanners for security. Finally, some challenging examples of satellite antennas are shown, such as spaceborne interferometer radars, contoured‐beam antennas for broadcasting, large inflatable reflectarrays, multibeam antennas for satellite communications, and high‐gain antenna for data transmission in CubeSats.