A modular stone stair system using a plurality of modules in the form of stringers, risers, treads and landings in standardized thicknesses and widths. The risers, landings (if any) and treads have different widths dependent upon the width of the stairs desired, with the treads and landing (if any) being of the full width of the stair, and the risers being a modular width such that each tread or landing is underlain by a plurality of risers. Each level of the stair has a plurality of stringers, abutting the back of the tread and riser and running to the back of the stair. The stringers vary in depth depending upon how many steps are to be present, such that each level, except the bottom, overlaps the tread and riser of the next lower level by a fixed amount. The system can easily be assembled by two people, using a shovel, a level, and a ruler, giving the homeowner or contractor the option of choosing threshold heights, widths, and landings with varying depths.