A recording tape cartridge includes: a case within which a reel wound with a recording tape is housed; a position-regulating hole that is formed in a lower surface of the case and into which a positioning member of a drive device is inserted; a reference surface formed around the position-regulating hole in the lower surface of the case; an allowance portion formed as a recess portion in an upper surface of the case, the allowance portion allowing an engaging member disposed at the drive device to advance therein and thereby preventing the engaging member from abutting against a front surface of the case when recording and playback of the recording tape cartridge is possible in the drive device; and a rear wall formed at the allowance portion, wherein a case-thickness-direction extended surface of the rear wall is positioned at least within a region of the reference surface.