Eric Chaz Custom refers to the custom instrument building work of Eric "Chaz" Czechanski, founder of Eric's Guitar Shop in Van Nuys, California. Czechanski began repairing and modifying guitars at age 12, started professional work in 1987, secured his business license in 1990, and opened his own shop in 1994. The shop operates out of the Sound City Center complex on Cabrito Road, the same facility that once housed the legendary Sound City Studios.

In addition to repair, modification, and setup work on guitars, basses, mandolins, banjos and ukuleles, Czechanski builds custom electric guitars and basses from scratch, producing roughly 30–40 instruments a year. Notable custom builds include a longhorn-shaped bass made for Kevin Rutmanis of the Melvins and Tomahawk. The shop has served a wide clientele of high-profile players and bands including Flea, John Frusciante, Steve Vai, John Mayer, Dave Matthews, Beck, Red Hot Chili Peppers, Tool, Nine Inch Nails, Rage Against the Machine, Foo Fighters, Paramore, and Arctic Monkeys.

The operation is small and hands-on, with Czechanski working alongside longtime team member Billy Butler. Output is more akin to a luthier's bench than a production shop, with one-off custom builds and heavily modified instruments forming the core of the Eric Chaz Custom output.

Eric Chaz Custom has 1 product cataloged on Equipboard, including Electric Basses. Their gear is featured by 1 artist, with the strongest followings in Rock. Notable users include Kevin Rutmanis.