An articulation system for chairs, the system comprising: - a frame designed to be associated with a base for a chair; - a support for a seat mounted on said frame; - at least one articulation element that is rigid and hinged to said frame so that it can rotate about an axis of rotation, wherein said support for the seat is hinged to said articulation element at a hinge point; - a support for a backrest, distinct from said support for the seat and coupled to said articulation element; wherein the articulation system further comprises, for each side, a pin that is firmly constrained to a front portion of said frame and a slot afforded in a front portion of the support for the seat, the pin slidably engaging the slot, wherein said articulation element and said pin and slot are configured in such a manner that said articulation system takes on an at-rest configuration, in the absence of tilting forces acting upon the support for the seat and/or upon the support for the backrest, and a maximum tilting configuration in which said support for the seat is rotationally translated with respect to the at-rest configuration, said pin sliding along said slot during the transition of the articulation system from the at-rest configuration to the maximum tilting configuration and vice versa, and wherein, in a reference plane perpendicular to said axis of rotation, an angle, defined as an acute angle formed between a tangent to the slot in an instant contact point between the slot and pin and a horizontal line, above the horizontal line, faces rearward, wherein said slot has a development at least partially curvilinear, characterized in that said angle gradually increases throughout at least a portion of movement of the articulation system from the at-rest configuration to the maximum tilting configuration. - a frame designed to be associated with a base for a chair; - a support for a seat mounted on said frame; - at least one articulation element that is rigid and hinged to said frame so that it can rotate about an axis of rotation, wherein said support for the seat is hinged to said articulation element at a hinge point; - a support for a backrest, distinct from said support for the seat and coupled to said articulation element; wherein the articulation system further comprises, for each side, a pin that is firmly constrained to a front portion of said frame and a slot afforded in a front portion of the support for the seat, the pin slidably engaging the slot, wherein said articulation element and said pin and slot are configured in such a manner that said articulation system takes on an at-rest configuration, in the absence of tilting forces acting upon the support for the seat and/or upon the support for the backrest, and a maximum tilting configuration in which said support for the seat is rotationally translated with respect to the at-rest configuration, said pin sliding along said slot during the transition of the articulation system from the at-rest configuration to the maximum tilting configuration and vice versa, and wherein, in a reference plane perpendicular to said axis of rotation, an angle, defined as an acute angle formed between a tangent to the slot in an instant contact point between the slot and pin and a horizontal line, above the horizontal line, faces rearward, wherein said slot has a development at least partially curvilinear, characterized in that said angle gradually increases throughout at least a portion of movement of the articulation system from the at-rest configuration to the maximum tilting configuration.