RainSong is a manufacturer of carbon fiber (graphite) steel-string acoustic guitars, credited with pioneering the all-composite acoustic. The company was founded by physicist Dr. John A. Decker Jr., who began developing composite guitars on Maui, Hawaii in the 1980s after observing how humidity and climate affected traditional wooden instruments. Operations later relocated to Woodinville, Washington for improved access to materials, craftspeople, and distribution.

The instruments are built around fully graphite bodies and necks, making them highly stable across temperature and humidity swings — a quality that appeals to touring and travel-oriented players. RainSong offers several body styles including the DR dreadnought, JM jumbo, OM orchestra, WS (Shorty), and PA parlor, organized into lines such as the Classic, Hybrid, Concert Hybrid, and Black Ice series. Proprietary construction techniques like Projection Tuned Layering were developed with Decker's son-in-law Ashvin Coomar to refine the soundboard's volume and low-end response.

Their sound is often described as bright and piano-like with sustained clarity, distinct from the warmer tonality of spruce or cedar-topped wood guitars. RainSong models are sold through specialty acoustic dealers and have been used by players drawn to the durability and tonal character of carbon fiber, including Jeff Pevar.

RainSong has 6 products cataloged on Equipboard, including Acoustic-Electric Guitars. Their gear is featured by 6 artists, with the strongest followings in Rock, Pop, and Metal. Notable users include Eddie van der Meer, The Backseat Lovers, and Jack Black.