Founded by John C. Koss in Milwaukee, Wisconsin, Koss is credited with inventing the first high-fidelity stereo headphone in 1958, fundamentally changing how people listen to music. What began as a side project from a hospital television rental business became a pioneering force in personal audio. The company went public in 1967 and by the mid-1970s controlled between 25 and 40 percent of the global stereo headphone market.

Koss is best known for the Porta Pro, an on-ear headphone introduced in 1984 that has achieved legendary status among audiophiles for its combination of lightweight portability, distinctive retro design, and remarkably rich sound at an affordable price point. The Porta Pro line has expanded to include wireless Bluetooth and communication headset variants, as well as the Utility series with interchangeable cord systems. Other notable products include the KPH30i on-ear headphone, the KTXPro1, the Pro/4AA studio headphone, and their electrostatic headphone line.

Headquartered in Milwaukee, Koss manufactures a range of headphones spanning on-ear, over-ear, earbuds, ear clip, wireless, noise-cancelling, and gaming headsets. The brand has a strong following in the audiophile community, where models like the Porta Pro and KSC75 ear clips are considered benchmark values in personal audio. Historically, artists such as Tony Bennett used Koss headphones, and the brand became standard equipment in recording studios and radio stations throughout the 1960s and 1970s.

Koss has 15 products cataloged on Equipboard, including Headphones & In-Ear Monitors. Their gear is featured by 8 artists, with the strongest followings in Rock, Pop, and Electronic. Notable users include Paul McCartney, Patrick Alavi, and Tony Bennett.