This is a writing instrument with a body (1) comprising a barrel (2) and a forward end piece (3) which has an outer surface (31). The barrel (2) has a forward end portion (22) that is at least partially covered by a trim member (4). The trim member (4) is prevented from rotating about a central axis (Z) relative to the barrel (2) and is continued by at least one elastically deformable tongue (44) which extends beyond the forward portion of the barrel. The outer surface (31) of the end piece (3) contains a hollow seat (36) extending from the base of this surface and designed to accommodate the tongue (44) when the end piece (3) is mounted on the end of the barrel (2).
