Stefan Stanisław Stec (November 21, 1893 - May 11, 1921) was a Polish aviator and military pilot, one of the pioneers of the Polish aviation. He is also credited as the designer of the Polish Air Force's insignia, the checkerboard.
Initially a military pilot in Austria-Hungary during the Great War. From 1916 he served as an observer in Flik 3 reconnaissance squadron on the eastern front. In February 1918 he himself trained as a pilot and from May he was assigned to Flik 3J fighter squadron, flying on Oeffag D.III on Austro-Italian front. Shortly, between June 17 and July 4 he commanded Flik 9J. He participated in shooting down 3 aircraft (plus 4 probable kills) and ended the war as Oberleutnant.
He was among the first pilots to join the Polish Air Force. From November 1918 he took part in the Polish-Ukrainian War, especially Battle of Lwów (1918). He carried out the first bombing sortie on November 7. Lataer he mostly flew on Fokker D.VII fighter. In 1919 he shot down a Ukrainian fighter Nieuport 11 and a balloon, becoming a fighter ace. From April to October 1919 he was a commander of the 7th Escadrille (later to be Kościuszko Squadron). Later he went to France to study in Ecole Superiore d'Aeronautique. After he came back, he was involved in starting the Polish aircraft production. He died in an aircrash in 1921.
His personal emblem from the time of Austrian service, a red and white checkerboard, was adopted on December 1, 1918 as the Polish Air Force roundel.