The Sikorsky S-39 is an American light amphibious aircraft produced by Sikorsky Aircraft during the early 1930s. The S-39 was a smaller, single-engine version of the S-38.

An amphibious aircraft or amphibian is an aircraft that can take off and land on both solid ground and water. They are typically fixed-wing, though amphibious helicopters do exist as well. Fixed-wing amphibious aircraft are seaplanes which are equipped with retractable wheels, at the expense of extra weight and complexity, plus diminished range and fuel economy compared to planes designed specifically for land-only or water-only operation. Some amphibians are fitted with reinforced keels which act as skis, allowing them to land on snow or ice with their wheels up.