A micromachined deformable mirror ((mu) -DMs) for optical wavefront correction is described. Design and manufacturing approaches for (mu) -DMs are detailed. The (mu) -DM employs a flexible silicon membrane supported by mechanical attachments to an array of electrostatic parallel plate actuators. Devices are fabricated through surface micromachining using polycrystalline silicon thin films. (mu) -DM membranes measuring 2 mm X 2 mm X 2 micrometers , supported by 100 actuators are described. Figures of merit include stroke of 2 micrometers , resolution of 10 nm, and frequency bandwidth DC - 7 kHz. The devices are compact, inexpensive to fabricate, exhibit no hysteresis, and use only a small fraction of the power required for conventional DMs. Performance of an adaptive optics system using a (mu) - DM was characterized in a closed-loop control experiment. Significant reduction in quasi-static wavefront phase error was achieved. Advantages and limitations of (mu) -DMs are described, in relation to conventional adaptive optics systems and to emerging applications of adaptive optics, such as high resolution correction, small aperture systems, and optical communication.