This article proposed an image segmentation algorithm based on Voronoi Diagram (VD). VD is a well-known technique in computational geometry, which generates clusters of intensity values using information from the vertices of the external boundary of Delaunay triangulation (DT). The image domain is partitioned into a group of sub-regions by Voronoi tessellation, each of which is a component of homogeneous regions. In this way, it is possible to produce segmented image regions. Voronoi-based image segmentation can be extended to RGB images without converting them into grayscale. Its mathematical formulation and practical implementations are also discussed and given. We test the method on and also compare it with K-means algorithms using segmentation examples; the results demonstrate excellent performance and competence of the proposed method.