GAMMA Custom Bass Guitars is a boutique bass builder based in Monmouth County, New Jersey, producing made-to-order electric basses since 2011. The company was founded out of frustration with off-the-shelf instruments, with the stated aim of delivering quality custom basses that are affordable and lightweight. Nearly every instrument is built to customer spec through their "Build Your Own GAMMA" configurator, though a small rotating stock of ready-to-ship basses is typically available.

The lineup centers on several core models including the Alpha (a J-style bass offered in configurations like the P16 Precision-style variant and J17 Special Edition), the Beta, and the Kappa, alongside fretless versions and the P19 Alpha. Instruments typically feature alder bodies, maple necks with matching maple fingerboards, block inlays with binding, and Tusq nuts, with a 34" scale on standard four-string models.

GAMMA sells direct through its own website and through a dedicated Reverb storefront, and the brand has been endorsed by working bassists including Adam Rigg, Jaymi Millard, Andy Irvine, Lil Asmar Johnson, and Emilio Rivas.

Gamma Custom has 2 products cataloged on Equipboard, including Solid Body Electric Guitars and Electric Basses.