This paper presents an efficient skeletonization method based on generalized discrete local symmetries. A generalized discrete local symmetry is a local symmetry between a contour pixel and a contour segment on the opposite side of the underlying shape. The centerlines of the local symmetries of a shape form the skeleton of the shape. The proposed method is fast compared to two existing skeletonization methods. A speed-up factor of more than 50 can be achieved for high-resolution images. The method is also robust against noise and geometrical transformations, such as rotation and uniform scaling. The method is suitable for skeletonizing high-resolution images where it can be impractical to use other skeletonization techniques, such as thinning and distance transforms, because of the high computational complexity.