Bladder stone is still a rare cause of obstetrical dystocia. We report a rare case of obstructed labour due to a huge bladder stone. Diagnosis was confirmed only at the time of cesarean section because of the unusual posterolateral location of the stone, which was impacted below the fetal head thus obstructing labour. A bladder stone weighing 140 g and measuring 9×6×5 cm3 was removed by cystolithotomy at the time of cesarean section. The postoperative period was uneventful.