Killer is a Japanese electric guitar and bass brand co-founded by Loudness guitarist Akira Takasaki and George Azuma. Manufactured and distributed in collaboration with ESP, the company builds instruments aimed at the heavy metal and hard rock market, with Takasaki himself responsible for many of the designs. The brand name was coined from a rearrangement of hiragana characters shared between Takasaki's given name and that of his guitar technician Ichizo Araki, phonetically rendered as "kiraa."

The lineup centers on a series of distinctive-bodied electric guitars including the KG-Prime, KG-Stallion, and KG-Pirates, along with basses and signature parts. Construction features associated with the brand include a VU-shaped neck profile and various through-body bracing and insert techniques intended for heavier playing styles. Killer also sells straps, hardware, and branded accessories through its own storefront and through Japanese retailers such as Ishibashi and BIGBOSS.

The brand has a close identity with Loudness and the Japanese metal scene more broadly, with many of its production models tied to Takasaki's stage instruments and anniversary models marking milestones in the band's history.

Killer has 10 products cataloged on Equipboard, including Electric Basses, Solid Body Electric Guitars, and Extended Range Guitars. Their gear is featured by 5 artists, with the strongest followings in Rock and Metal. Notable users include Toshiya, Taiji Sawada, and Akira Takasaki.