A process for detecting a derailment of a rail vehicle having two or more rail vehicle parts and one or more articulations through which adjacent rail vehicle parts are rotatably connected with one another includes determining an angle of rotation between adjacent rail vehicle parts, and/or a quantity derived from the angle of rotation. The process further includes comparing the angle of rotation or the derived quantity with at least one reference value or threshold, or with at least one reference value range or threshold range. A test criterion indicating whether or not there is a derailment is defined based on the at least one reference value or threshold, and/or an expected relationship of multiple angles of rotation, and/or an expected relationship of the multiple quantities derived from the angles of rotation, relative to one another. The method further includes determining whether or not the test criterion is met.