Abstract: The present invention relates to a flexible insulating panel for an out-of-ground swimming pool, the latter comprising vertical structural ribs that radially outwardly protrude therefrom. The panel comprises a substantially rectangular insulating foam liner encased in a protective jacket. The panel defines an inner surface abutting on the outer surface of the pool peripheral wall and a water-resistant outer surface. The panel is correctly dimensioned and adapted to fit between two consecutive ribs, a plurality of panels thus being installed in a peripheral consecutive manner along the peripheral wall of the pool. The jacket of the panel has two flanges that extend tangentially, relative to the pool peripheral wall, each flange straddling the flange of the next panel, adjacent to and over the rib between the two of them.