Wave winding coil for an internally or externally slotted laminated stator core of an electrical machine, comprising a plurality of electrical conductors (11a-11l) of wavelike form, wherein each of the plurality of electrical conductors (11a-11l) has a plurality of wire segments arranged running in parallel; wherein the wave winding coil can be arranged on the laminated stator core in such a way that several or all of the wire segments arranged in parallel can be introduced into stator slots of the laminated stator core; wherein the wave winding coil, in the state when not arranged on the laminated stator core, takes the form of a planar coil; and wherein it is provided that, for insertion into an internally or externally slotted laminated stator core, the wave winding coil is curved to form a substantially cylindrical coil body, characterized in that in the state when not arranged on the laminated stator core, the wave winding coil has a variable slot pitch so that at least a first distance and a second distance of two respective wire segments differ from one another in a first direction which, in the state of the wave winding coil arranged on the laminated stator core, corresponds to a circumferential direction of the laminated stator core, said wire segments being arranged adjacently and to be inserted into adjacent stator slots, wherein the first distance and the second distance are measured in the first direction, wherein, depending on the arrangement and winding scheme of the wave winding coil, the adjacent wire segments are wire segments of the same electrical conductor (11a-11l) or are adjacent wire segments of different electrical conductors (11a-11l), wherein the wave winding coil has at least two segments (22a-22f) along the first direction; wherein each of the segments (22a-22f) has a plurality of parallel-running wire segments of the plurality of electrical conductors; wherein each of the segments (22a-22f) has a constant slot pitch; wherein the slot pitches of at least two segments (22a-22f) differ; wherein each segment (22a-22f) of constant slot pitch in the state when arranged on the laminated stator core corresponds to one revolution of the wave winding coil around the inner circumference or around the outer circumference of the laminated stator core; and wherein the constant slot pitch in each segment (22a-22f) corresponds to that slot distance which is measured in depth in the stator slot in which the wire segments arranged in parallel and corresponding to the respective revolution come to lie. in the state when not arranged on the laminated stator core, the wave winding coil has a variable slot pitch so that at least a first distance and a second distance of two respective wire segments differ from one another in a first direction which, in the state of the wave winding coil arranged on the laminated stator core, corresponds to a circumferential direction of the laminated stator core, said wire segments being arranged adjacently and to be inserted into adjacent stator slots, wherein the first distance and the second distance are measured in the first direction, wherein, depending on the arrangement and winding scheme of the wave winding coil, the adjacent wire segments are wire segments of the same electrical conductor (11a-11l) or are adjacent wire segments of different electrical conductors (11a-11l), wherein the wave winding coil has at least two segments (22a-22f) along the first direction; wherein each of the segments (22a-22f) has a plurality of parallel-running wire segments of the plurality of electrical conductors; wherein each of the segments (22a-22f) has a constant slot pitch; wherein the slot pitches of at least two segments (22a-22f) differ; wherein each segment (22a-22f) of constant slot pitch in the state when arranged on the laminated stator core corresponds to one revolution of the wave winding coil around the inner circumference or around the outer circumference of the laminated stator core; and wherein the constant slot pitch in each segment (22a-22f) corresponds to that slot distance which is measured in depth in the stator slot in which the wire segments arranged in parallel and corresponding to the respective revolution come to lie.