Altero Custom Guitars is a guitar workshop based in Otsu, Shiga Prefecture, Japan, founded in 2010 by craftsmen who previously taught and worked as repair technicians at a specialized guitar craft school. The shop combines custom instrument building with a high-volume repair and modification practice, and also operates a retail storefront carrying used instruments and accessories.

The builder's catalog centers on three original models — the Astra, Vuoto, and Avvolge — alongside fully bespoke commissions for both guitars and basses. Builds often feature premium appointments such as Bare Knuckle, Seymour Duncan, or EMG pickups and tonewoods including roasted maple, Hawaiian koa, and Brazilian rosewood. Altero also produces a small line of effect pedals, including the KAEDE, Wal Overdrive, and Mag Distortion, developed in collaboration with KarDiaN designer Toshikazu Kitada.

The workshop's output is hand-made in Japan and tends to be discussed in the context of the country's boutique luthier scene, with a reputation built on detailed fretwork and the sheer volume of repair experience feeding back into the custom builds.

Altero Custom Guitars has 9 products cataloged on Equipboard, including Solid Body Electric Guitars, Overdrive Effects Pedals, and Semi-Hollowbody Electric Guitars. Their gear is featured by 2 artists, with the strongest followings in Rock. Notable users include Tricot and SUNAO.