Open-end spinning unit with a spinning rotor having a lower side and an upper side. A lid is inserted into a front opening provided in said lower side, said lid being bored so as to form a fiber supply duct to convey separated fibers into the interior of said spinning rotor. A yarn take-off duct extends through said upper side of the spinning rotor and conveys the yarn via an outlet port out of the interior of the spinning rotor. A separator is secured to said lid and is designed to divide the rotor interior into a fiber supply zone and a yarn producing and take-off zone. The front surface of said separator which faces said yarn take-off duct constitutes a directing wall for directing the yarn end being returned to be spun-in, the circumferential edge of said directing wall being located in a space defined by a pair of planes perpendicular to the spinning rotor axis, one of said planes passing through the maximum yarn producing and take-off zone diameter and the other plane being spaced 6 mm therefrom in the direction toward the yarn take-off duct.
