Section insulator for an overhead contact line arranged for being placed between two isolated sections of said overhead contact line, said section insulator having an insulating element placed between two contact wires of two adjacent sections of an overhead line; two clamps respectively connected on one side to a respective contact wire and on the other side to a connecting plate arranged for being in turn connected to the insulating element, so that the tensile force due to the contact wires applies along the axis of the insulating bar; and supporting means directly connected to the insulating element through the connecting plates and arranged for supporting the section insulator to the overhead line.