Landslide is one of the most hazardous natural disasters in the Himalaya region causing hundreds of deaths in Nepal every year. In this study, a slope stability analysis on a regional scale is presented for an area of 347 sq. km. of Dhading district, Nepal. A physically based slope stability model coupled to a simplified groundwater flow model is used to estimate soil wetness index, and factor of safety maps are produced for three steady state scenarios (completely dry, half-saturated, and completely saturated soils) and one quasi-dynamic scenario (soil wetness resulting from extreme daily rainfall events with return periods of 25 years) with both methods based on infiltration and contributing area. These maps can be of great help to engineers and planners for choosing suitable locations to implement developments and can be used as basic data to assist slope management and land-use planning. The present results also provide useful information for possible improvements in disaster management activities.