The major difference between pedestrian flow and lane-based vehicular traffic is the dimensionality: pedestrians can move in any direction which makes the modeling significantly more demanding. For the macroscopic models, this means a specification of a velocity vector field in form of partial differential equations with the independent variables x, y, and t which are only used for unidirectional flows. General pedestrian flows are the domain of microscopic models and we devote the main part of this chapter to its main representative, the Social Force Model by Helbing and Molnár. Besides the basic model, we include several variants, an extension to physical forces and give simulation recommendations. We also present two alternative microscopic approaches, namely an iterated map based on the human principle of least effort, and a generic approach to modeling pedestrian flows by cellular automata.