Abstract: The modular wall structure for underground swimming pools comprises a number of wall panels each comprising an upright portion defining opposite inner and outer sides, opposite first and second edges and opposite top and bottom ends. The wall panel also has a shelf portion generally perpendicular to the upright portion and attached thereto at the top end in cantilevered fashion. The wall panel includes an inclined bracing portion linking the outer side of the upright portion to the shelf portion in an inclined fashion. The wall panel further has complementary attachment members provided on the upright portion first and second edges to allow the wall panel to be edgewisely attached at its first edge to the second edge of an adjacent the wall panel and along its second edge to the first edge of an adjacent the wall panel.