In this chapter, the focus moves from a single robot performing a task in free space or physically interacting with the environment to the case of multiple robots manipulating a common object. First, the case of a multi-arm system composed of rigid robots tightly grasping a rigid object is considered. Kinematics, statics, and dynamics of the cooperative system are analyzed, taking into account the geometric constraints imposed on the joint variables of the manipulators in view of the tight grasp/rigid object assumption. In particular, the concepts of grasp matrix and of internal and external object wrenches are introduced, as well as the equations of the augmented object in task space, describing the dynamics of both object and robots. Then, the main control strategies for the motion of the cooperative system and the interaction forces between the manipulators and the grasped object are presented. In the second part of the chapter, the principles involved in the study of cooperative manipulators are extended to the problem of grasping an object using a multifingered hand, where the fingers of the hand are seen as multijoint structures cooperatively handling an object. The main difference between the two problems is that in multifingered manipulation only some motion and force components are transmitted to the object through each contact and object grasping is not guaranteed. The basic contact models in the presence of friction are introduced, relying on the standard Coulomb friction model, when present. This motivates the definition of a hand Jacobian which, along with the grasp matrix, respectively, maps only the transmitted components of the twists and contact wrenches. The mathematical grasp properties of these mappings give rise to five primary grasp classes whose physical interpretations provide insight for grasp and manipulation planning. Finally, the definitions of form closure and force closure, to guarantee grasp maintenance in the absence and in the presence of contact friction, are given.