The invention relates to a guide plate for laterally guiding a rail S for rail vehicles to be fastened to a base 2 by means of a spring element 13 having a front face, against which the rail S is supported in the mounting position, and having an insulator element 19 which can be placed onto the foot F of the rail to be fastened, via which insulator element 19 the spring element 13 in the mounting position acts on the foot F of the rail S. The invention also relates to a system for fastening a rail, which comprises such a guide plate 3. In order to simplify mounting and to ensure reliable, correct positioning of the insulator element even under unfavourable mounting conditions, the invention makes provision for the insulator element 19 to be mounted on the guide plate 3 so that it can pivot.