Abstract: The flexible contour wheelchair backrest comprises two side posts, and a flexible backrest body extending between the two side posts. The flexible backrest body comprises a plurality of transversally extending and vertically spaced apart flexible straps each interconnecting the two side posts and each having an adjustable length, and a plurality of substantially stiff and malleable stays intersecting at least one of the flexible straps at right angle. Each side post defines an elongated curved front face for receiving the flexible backrest body. This elongated curved front face has a forwardly bulging section for inducing a depth dimension to the flexible backrest body to fit the posterior lateral contour of a user's back and thereby provide lateral support to the user's trunk. A mechanism is used to adjust the distance between the forwardly bulging sections of the elongated curved front faces.