Abstract: A coupling device for fluid lines includes a female part having a rotatable locking arm with a cam, and a male part defining a longitudinal channel and a circumferential groove on its external surface. The male part is inserted into the female part by rotating the locking arm to its unlocked position, aligning the longitudinal channel with the cam, and sliding the cam within the longitudinal channel. The male part is locked into the female part by rotating the cam within the circumferential groove away from the longitudinal channel, and rotating the locking arm into its locked position so that the cam protrudes further into the circumferential groove. Even when the locking arm is rotated to its unlocked position, the cam engages the circumferential groove to retain the male part within the female part unless the cam is rotated within the circumferential groove into alignment with the longitudinal channel.