Sylvania Electric Products was an American electronics manufacturer headquartered in Emporium, Pennsylvania, and one of the dominant U.S. vacuum tube producers of the 20th century. The company traces back to 1901 and took shape as Hygrade Sylvania Corporation through a 1931 merger of Nilco Lamp Works, Sylvania Products Co., and Hygrade Lamp Company. In the receiving-tube market, Sylvania stood as RCA's principal domestic rival, supplying both consumer and military-grade (JAN — Joint Army Navy) tubes.

In the music gear world, Sylvania is prized for its new-old-stock (NOS) vacuum tubes, which remain staples in vintage guitar amplifiers and high-end audio. The 12AX7 preamp tube is the most celebrated example, produced in several distinct constructions — long black plate (late 1940s), long grey plate (1960s–early '70s), short plate, and ribbed plate variants — each with its own sonic character. Sylvania 12AX7s are commonly associated with clean, articulate tone and extended top end, and often appear in blackface-era Fender amps such as the Twin Reverb. Sylvania-branded 6L6, 6L6GB, 6V6, 5U4, and 5AR4 power and rectifier tubes are similarly sought after by amp builders and restorers.

Sylvania tubes manufactured during the 1950s and 1960s are generally considered the brand's peak, with carbonized-nickel plates, mirror-finish getters, and optical-quality mica spacers. While RCA, Mullard, and Telefunken tend to receive more attention in the NOS market, Sylvania holds a strong reputation among amp techs and audiophiles as a high-quality, often more accessible alternative.