A new sponge species of the genus Hymeniacidon (family Halichondriidae) from Munsum, Jeju Island, Korea is described. This species is similar to H. sinapium in spicule size, but the color, oscules, external surface and arrangement of the spicules are considerably different. This species is bright yellow in live, and retains multiple oscules and a plumose bundle of styles in the subectosomal region.