The Fokker S.IV was a military trainer aircraft produced in the Netherlands in the mid-1920s. It was a conventional, single-bay biplane with staggered wings of unequal span braced with N-struts, essentially a radial-engined development of the S.III. The pilot and instructor sat in tandem, open cockpits and the undercarriage was of fixed, tailskid type with a cross-axle between the main units. The Royal Netherlands Army Aviation Group purchased 30 examples and used them right up to the German invasion of the Netherlands in 1940. On 14 May that year, a few surviving S.IVs escaped to France alongside some S.IX trainers, but never flew again.