A collapsible chassis for strollers includes a base frame supporting at least one front post and at least one rear post with wheel assemblies. The base frame further supports at least one handle tube. An actuation element is supported by the base frame and is actuated by the user to move the chassis from the open condition to the closed condition. The actuation element is movable with respect to both the handle tube and the movable post and is connected by way of a first kinematic connection element to the movable post and by way of a second kinematic connection element to the handle tube. Actuating the actuation element causes the rotation of the movable post and handle tube. A third kinematic connection element is provided which includes an articulation element adapted to cause a motion of mutual approach in a transverse direction of the two rear posts.