Seizi is a Brazilian musical instrument brand associated with luthier Seizi Tagima, who is also known as the founder of the separate Tagima company. Distributed in Brazil by Royal Music, the brand offers a broad catalog spanning electric guitars, bass guitars, acoustic guitars (violões), ukuleles, and accessories such as cables, straps, and cases.

The lineup leans toward affordable instruments with vintage-inspired designs and Japanese-themed branding. Bass models like the Seido draw on Precision Bass styling, while the ukulele range includes the Bora-Bora, Maui, Bali, and Kauai series along with a U-Bass. Acoustic guitars are split into Originals and Supreme lines, the latter featuring solid tops, rosewood fretboards, and Fishman electronics. Many electric models use the brand's Mirai pickups, and selected basses ship with proprietary Seizi Jutsu Alnico V pickups.

Accessories are grouped under named lines such as Energy cables and Armor cases. The brand has a strong retail footprint across Brazilian music shops and is most visible domestically rather than internationally.

Seizi has 5 products cataloged on Equipboard, including Solid Body Electric Guitars. Their gear is featured by 1 artist, with the strongest followings in Rock and Metal. Notable users include Andreas Kisser.