A recording tape cartridge includes: a reel having a cylindrical hub with a bottom and a reel gear formed therein with recording tape wound therearound; a casing; a brake component; and a releasing component that is provided between the bottom of the hub and the brake component and which has plural legs inserted through plural through-holes formed on the reel gear where, when in use, the plural legs are pressed upwards by a drive gear of a drive device, whereby the releasing component lifts the brake component, releases engagement with the engaging portion and rotates with the reel. The legs are formed into approximate D shapes in plan view whose outer side surfaces facing an inner peripheral surface of the hub are flat surfaces, while the through-holes are formed into approximate D shapes in plan view through which the legs can each be inserted.