A writing instrument that includes a barrel extending along a longitudinal axis (A) and a tip mounted at the front of the barrel, further including a protective sleeve for the tip, the sleeve being mounted coaxially on the barrel and movable relative to the barrel between a protective position where it covers the tip and a retracted position where it exposes the tip to allow writing. The sleeve includes an inner wall which includes a helical cam engaging with a guide element formed on the barrel so that the sleeve is movable in translation combined with rotation.