Onerr was a Brazilian manufacturer of guitar effects pedals that operated until around 2004–2005. The company initially produced pedals under license from Roland Japan, with its first wave of units consisting of direct copies of Boss designs, housed in solid all-metal enclosures. After Boss established its own presence in the Brazilian market and reclaimed its licensing arrangements, Onerr shifted to designing its own circuits, resulting in a second wave of pedals that drew on familiar Boss-style layouts and voicings but were developed in-house.

The brand is best known for its Tungsten series of overdrive and distortion pedals, including models such as the TO-1 Tungsten Overdrive, TD-1 Tungsten Overdrive, and the TO-3 Tungsten DriveMaster — a three-band EQ overdrive offering Blues, Hi-Gain, and Metal drive modes. Onerr's catalog also spanned delay, chorus, and other common effect types, often mirroring the format and control layout of comparable Boss compact pedals.

Because production ceased more than a decade ago and Onerr pedals were primarily sold within Brazil, they are uncommon on the international used market and have developed a small collector following. They are typically traded through secondhand marketplaces such as Reverb and discussed in gear forums like TalkBass and Harmony Central, where players note their build quality and Boss-adjacent tones.

Onerr has 14 products cataloged on Equipboard, including Combo Guitar Amplifiers, Overdrive Effects Pedals, and Distortion Effects Pedals.