Abstract: A chair seat cushion for use with a chair having a backrest, as well as a chair fitted with such a cushion, that improves seating comfort and reduces load on the user's lumbar region. The cushion has a bevelled front edge and a bevelled concave rear edge. The length of the cushion is such that, when properly placed on the seating surface of a chair for use, the user's knees and calves are in front of and out of contact with the front edge, while the user's hips are in generally vertical alignment with the rear edge such that the user's buttocks extend behind the rear edge. With the user's back supported by the backrest, the user's weight is largely supported on the thighs, thereby reducing lumbar load.