Abstract: A coupling device (1) for connecting and/or closing off fluid lines (60) includes: a male coupling element (2) having a continuous recess (5) provided around the outer circumference and one radial projection (6); a female coupling element (3) having an arm (9) which includes, at one end, an operating element (10) and, at an opposite end, at least one radially extending locking element (11). The female coupling element (3) further includes a slot (108) that extends in axial direction and is a breather duct when the arm (9) is in the first position; a bayonet fastening which is formed by a labyrinth-like guide (12) in the wall (7) of the female coupling element (3) and the radial projection (6) of the male coupling element (2). Also described are a line path and a line end section in which the coupling device has been accommodated.