A tow bar for an agricultural tractor comprises an end fork (16) in which are formed two axially aligned holes, an upper hole (22) and a lower hole (23), for a tow pin (24) which is selectively mobile between an engagement position, in which the tow pin (24) extends through the mouth (20), and a disengagement position, in which the tow pin (24) is retracted into the upper hole (22) only. Means (40) for restraining the tow pin (24) interact with a lower portion (24a) of the tow pin (24) in order to keep it raised, and they are selectively unlockable owing to the action of control means (37) to permit the descent of the tow pin (24) into the engagement position.
