An all-reflective afocal optical system including an aspheric beam steering mirror positioned at an exit pupil of the afocal optical system. In one example, an all-reflective afocal optical imaging system includes a sensor, a afocal optical apparatus including a plurality of mirrors optically coupled together and configured to receive light rays through an entrance pupil of the afocal optical imaging system and to substantially collimate the light rays to provide a collimated optical beam to an exit pupil, and an aspheric beam steering mirror positioned at the exit pupil and configured to receive the collimated optical beam and to direct the collimated optical beam to the sensor.