A guide rail (1) of a linear guide, on which a guide carriage (2) can be mounted longitudinally displaceably, the guide rail (1) having an underside, by means of which it can be arranged on a mounting surface (3), and two opposite longitudinal sides which are provided with running tracks (8), rail parts (10) of the guide rail (1) which are arranged one behind the other being connected to one another by means of connecting elements (13, 21), a tension element (19a) being provided in order to brace the connected rail parts (10) with respect to one another.