<p>In order to allow for a greater degree of freedom in the design of a security tag and to reduce the costs associated with the production of a recording tape cartridge, a recording tape cartridge (10) comprises: a case (12) housing a reel (20) on which is wound a recording tape (T); a columnar security tag (110) that is provided in the case (12) and is capable of transmitting signals to and receiving signals from the outside; a holding member (120) that is provided in the case (12) and has a holder formed in one end thereof in a manner such that the holder and the case (12) hold the security tag (110) from the axial direction of the rail (20) and from a direction orthogonal to the axial direction; and an engagement part (15) that is engaged by an engaging part (124) formed at the other end of the holding member (120) is formed in the case (12).</p>
