The SPAD S.XX, also known as the S.20, was a French biplane fighter developed shortly after World War I. Designed by Louis Béchereau, the aircraft was intended as an improvement over the successful SPAD S.XIII, incorporating more advanced features and benefiting from lessons learned during the war.

Introduced in the early 1920s, the S.XX retained the robust, streamlined characteristics that had defined earlier SPAD fighters but featured refinements in aerodynamics and structure. It was powered by a Hispano-Suiza engine and equipped with synchronized forward-firing machine guns. The aircraft had a relatively short wingspan and a compact fuselage, maintaining the emphasis on speed and durability that had made its predecessors popular with aces.

Although the S.XX was produced in limited numbers, it was adopted by the newly formed French Air Force and a few other countries. However, it came at a time when military aviation was transitioning rapidly. As such, it was soon overshadowed by newer monoplane designs and advances in aviation technology, marking it as one of the last in the line of classic SPAD biplanes before the interwar period saw a shift toward more modern aircraft.

While not as iconic as the SPAD S.XIII, the S.XX represents an important link between World War I-era designs and the evolving air power of the 1920s.