This thesis investigates a novel deformable mirror that works on the basis of the electrostatic deformation of a liquid surface. The liquid mirror allows large surface displacements, a large number of actuators, and the modification of its properties, while at the same time the mirror design is simple and may be realized without sophisticated technology. The mirror is capable of dynamic wavefront correction, fine imaging, and spatial light modulation. The mirror is demonstrated to be a low-cost versatile tool for Adaptive Optics that can be implemented for less than 100 Euro.