A writing instrument includes a cylindrical barrel and an end cover having a robust structure and attached to the cylindrical barrel. The end cover includes a cylindrical base attached to a rear end portion of the cylindrical barrel, a cover body fitted around an outer peripheral surface of the cylindrical base, a stopper ring fitted around an outer peripheral surface of at least a fitted portion between the cylindrical base and the cover body, and a cooperation structure for enhancing a holding force which is exerted on the cover body by the cylindrical base and the stopper ring and for joining the cylindrical base, the cover body, and the stopper ring together to form a joined unit which includes the cylindrical base, the cover body and the stopper ring.