Vinylon, also known as Vinalon (more common in Korean sources), is a synthetic fiber produced from reaction between polyvinyl alcohol (PVA) fiber and formaldehyde. Chemically it is polyvinyl formal (PVF). Vinylon was first developed in Japan in 1939 by Ichiro Sakurada [ja], Ri Sung-gi, and H. Kawakami. In North Korea, Ri Sung-gi found a route to produce PVA from domestic anthracite (black coal) and limestone as raw materials. Trial production began in 1954 and in 1961 the massive "Vinylon City" was built in Hamhung, North Korea. Vinylon's widespread usage in North Korea is often pointed to as an example of the implementation of the Juche philosophy, and it is known as the Juche fiber.

PVF, in fiber form, is a useful thermoplastic resin on its own, most commonly used as electric wire insulation.

Vinylon is the national fiber of North Korea and is used for the majority of textiles, outstripping fiber such as cotton or nylon, which is produced only in small amounts in North Korea. Other than clothing, vinylon is also used for shoes, ropes, and quilt wadding.

Japanese-Canadian textile artist Toshiko MacAdam used vinylon in her early works, as it was more economical than nylon.

Swedish outdoor brand Fjällräven makes their popular Kånken backpack line out of a version of vinylon, branded Vinylon F.

Vinylon is resistant to heat and chemicals but has several disadvantages: being stiff, having a relatively high manufacturing cost, and being difficult to dye.

The production process by Ri is as follows:

Other locations may use alternative feedstocks to synthesize PVOH.