AlgoMesh is a software tool providing implementations of two complementary algorithms for generation of unstructured triangular and Voronoi grids. It incorporates a comprehensive, easy-to-use graphical user interface (GUI) to assist in the model-building process. AlgoMesh's primary focus as a model-building tool is producing input files for MODFLOW-USG, MODFLOW 6 and HydroGeoSphere™ simulations. However, its two-dimensional grid generation capabilities are quite general and it may be used as a powerful standalone mesh generator for any purpose. The following sections of this guide present a summary of the grid generation capabilities of AlgoMesh and its user interface functionality.