The ASW 20 is an FAI 15 metre Class glider designed by Gerhard Waibel and built by Alexander Schleicher GmbH & Co. Its fuselage is nearly identical to that of the ASW 19, mated to newly designed flapped wings for the 15 metre Class.

Roy McMaster, Karl Striedieck and John Seymour won jointly, with others, the world triangle distance record of 1,435 km (892 mi) in 1994 in an ASW 20B.

Centrair also produced an FL variant equivalent to the German ASW20L; most of these are only permitted to fly without the wingtip extensions due to a deficiency in the wing spar construction.

This concept is known as the Katzmayr Effect, and somewhat mimics a bird's ability to use a flapping motion to propel itself forward in flight.

This unique wing twisting movement gave the ASW-20 an ability to make very small but consistent performance gains (or reduced losses) in turbulent and gusty thermal conditions compared to other competition level sailplanes.

The flexible wing of the A and C models is particularly favored for ridge running, where it absorbs some of the tremendous turbulence found at ridgetop.