S39 may refer to:
Aviation Blériot-SPAD S.39, a French reconnaissance aircraft Letov Š-39, a Czechoslovak sport aircraft Prineville Airport, in Oregon, United States Sikorsky S-39, an American flying boat
Other uses S39: Wear eye/face protection, a safety phrase New Jersey Route 68, designated Route S39 until 1953 Sulfur-39, an isotope of sulfur , a submarine in the United States Navy