Active optics has been proposed for application to space telescopes since the mid 1960s since it can help to relax manufacturing tolerances while guaranteeing diffraction-limited image quality, correct for thermal gradients and any errors due to launch loads. The James Webb Space Telescope, which will be segments, will incorporate active optics to ensure alignment of the segments as well as controlling segment shape. Monolithic mirror space telescopes have been proposed incorporating active control, either acting on the primary mirror or at a relayed pupil. This paper provides a historical review of Active Optics, with emphasis on the application to Space Telescopes concluding with some results of a laboratory prototype system developed for the European Space Agency.