Network Simulators are important tools in network research. As the selected topology often influences the outcome of the simulation, realistic topologies are required to produce realistic simulation results. The topology generator presented in this document, GenSeN, was created based on the authors’ knowledge from several experiences. GenSeN is a tool capable of generating realistic topologies of wireless sensor networks and, additionally, auto-configuring important characteristics of sensor nodes, such as energy parameters. The tool was validated by comparison with real deployment strategies and experiences.