The Letov Š-18 was a Czechoslovak single-engined, two-seat biplane trainer. It was designed by Alois Smolík at Letov Kbely. The Š-18 first flew in 1925. The aircraft was quite successful and sold well, both to private pilots and to flying clubs. Apart from the basic variant, there was also still the type Š-118, which was equipped with a Walter NZ-85 engine (85 hp, 63 KW). Some machines were exported to Bulgaria. The Czechoslovakian Air Force used the type 1925 to 1930 as a beginner trainer aircraft.