Writing instrument

A writing instrument (1), which is formed as a pushbutton writing instrument comprising a writing instrument housing (3), with a writing tip (8) protruding beyond one end of said housing, said writing tip being movable by a pushing mechanism between a writing position, projecting beyond one end of the writing instrument housing (3), and a standby position, located in a housing interior of the writing instrument housing (3), the pushing mechanism being actuatable by a pushbutton (5) that is a functional element, which is provided at a second end of the writing instrument housing (3) that is remote from the writing tip (8), the pushbutton (5) includes a first pushbutton subregion (9) that is displaceably guided in the writing instrument housing (3) and having a first finger-engagable region that protrudes beyond the second end of the writing instrument housing (3) and a receiving opening (10) that extends to a region within the writing instrument housing, the first pushbutton subregion (9) is in driving connection with the pushing mechanism, a second pushbutton subregion (6) is detachably fastened to the first pushbutton subregion (9), the second pushbutton subregion (6) including a second finger-engagable region that protrudes beyond the second end of the writing instrument housing (3) and is complementary to and engagable with the first finger-engagable region to form an external portion of the pushbutton, and a machine-readable data memory connected to the second finger-engagable region and removably insertable into the receiving opening (10) such that the machine-readable data memory extends within the writing instrument housing (3), and the first finger-engagable region allowing actuation of the pushing mechanism upon removal of the second pushbutton subregion (6).