This paper applies a three-dimensional formulation to define the safety factor. The problem analysis uses a 3D limit equilibrium model of slope stability considering the action of rainfall by infiltration models able to simulate advancing wetting front and the change in the groundwater table due to a given rainfall event. Additionally, the probability of failure was obtained by using a probabilistic method that inserts the variability of certain soil parameters and provides the probability distribution of the safety factor. The methodology has been applied to map the landslides hazard triggered by rains in a region of the Federal District, Brazil, considered to have a high potential for the occurrence of such events. As a result, maps of the spatial distribution of probability of failure were achieved, making it possible to distinguish the condition of slope stability in this study.