A writing instrument that includes a sleeve-like housing, a reservoir axially extending in the housing, a push button positioned in the rear portion of the housing, a latching device for latching the push button in a writing position with a latch recess in the housing and a latch lug positioned at the free end of a transversely elastically bendable spring arm extending from the push button. The writing instrument also includes a shift device for releasing the latching device and returning the latch lug into a parking position, and a support member disposed at the push button that includes a support surface which stops the latch lug from lateral movement into the latch recess when being moved back from a position moved forward beyond the writing position. In order to enhance the arrangement of the support member in the writing instrument, the support member is disposed at a peripheral wall portion of the push button.