A knife sheath, comprising: a receptacle with an opening for receiving and enclosing a blade of a knife which is introduced into the receptacle along a longitudinal axis of the receptacle, an attachment piece for suspending the knife sheath from a user, and a collar (9, 9') which is detachably attached to the receptacle at the opening, wherein an edge receiving portion of the collar (9, 9') is provided with a sharpener which may provide a sharpening action to a blade of a knife which is introduced into the receptacle through the opening, the collar (9, 9') is provided with a first and second opposite outer side surface, the first outer side surface is provided with a first flexible protrusion with an outer end protruding outwards from the first outer side surface, and the second outer side surface is provided with a second flexible protrusion with an outer end protruding outwards from the second outer side surface, and the receptacle is provided with a first and second inner side surface with a respective cavity for receiving the outer ends of the first and second flexible protrusions (18, 19) for attaching the collar to the receptacle, characterized in that the receptacle and the collar are shaped to allow the collar and receptacle to be attached to each other in a first position and in an alternative second position such that in the second position the receptacle has been turned around the longitudinal axis of the receptacle as compared to the first position, wherein in the first position the attachment piece is located on the left side of a knife whose edge is received by the edge receiving portion of the collar (9, 9'), and in the second position the attachment piece is located on the right side of a knife whose edge is received by the edge receiving portion of the collar (9, 9'). a receptacle with an opening for receiving and enclosing a blade of a knife which is introduced into the receptacle along a longitudinal axis of the receptacle, an attachment piece for suspending the knife sheath from a user, and a collar (9, 9') which is detachably attached to the receptacle at the opening, wherein an edge receiving portion of the collar (9, 9') is provided with a sharpener which may provide a sharpening action to a blade of a knife which is introduced into the receptacle through the opening, the collar (9, 9') is provided with a first and second opposite outer side surface, the first outer side surface is provided with a first flexible protrusion with an outer end protruding outwards from the first outer side surface, and the second outer side surface is provided with a second flexible protrusion with an outer end protruding outwards from the second outer side surface, and the receptacle is provided with a first and second inner side surface with a respective cavity for receiving the outer ends of the first and second flexible protrusions (18, 19) for attaching the collar to the receptacle, characterized in that the receptacle and the collar are shaped to allow the collar and receptacle to be attached to each other in a first position and in an alternative second position such that in the second position the receptacle has been turned around the longitudinal axis of the receptacle as compared to the first position, wherein in the first position the attachment piece is located on the left side of a knife whose edge is received by the edge receiving portion of the collar (9, 9'), and in the second position the attachment piece is located on the right side of a knife whose edge is received by the edge receiving portion of the collar (9, 9').