Abstract: A modular spa cover for covering the opening of a spa enclosure is provided. The spa cover can have a first inflatable panel, a second inflatable panel, and an insert panel. The first inflatable panel can be coupled to the second inflatable panel in the absence of the insert panel to form an assembled configuration, or the first and second inflatable panels can be coupled to the insert panel to form an augmented assembled configuration. When coupled, the interconnects between the panels can be flexible to permit rotation of each panel with respect to the other panels. The panels can include side skirts to cover a gap between the spa cover and the upper surface of the spa. The panels can be formed from drop stitch technology and can include inflation/deflation valves, pressure relief valves, handles, and/or tethering straps.