The recording tape cartridge includes a case body formed by joining together an upper half and a lower half and a tape reel around which a recording tape is wound. The cartridge further includes a lid covering a front side of the case body, and a reel lock member which has a braking claw to be engaged with an engagement tooth provided on a flange of the tape reel and which is adapted to slide with rotation of the lid. Ribs nip the reel lock member so as to perform positional regulation, and a sliding reel lock member urging device urges the reel lock member so as to engage the braking claw with the engagement tooth. A reel lock releasing member urges the reel lock member with rotation of the lid so as to release the engagement.