A chair seat for flexibly supporting the buttocks of a user seated thereon. The chair seat includes a seat surface having a pair of adjacent or side-by-side concentric corrugated regions formed therein, and which are configured for flexibly supporting the buttocks of the user by being deflectable with respect to the seat surface. The seat surface further includes a third corrugated region surrounding and concentric with the pair of side-by-side corrugated regions, and which third region is configured for flexibly supporting the hips and thighs of the user while also being deflectable with respect to the seat surface.