Keilwerth is a German saxophone manufacturer founded in 1925 by Julius Keilwerth and his brother Max in Graslitz, then part of Czechoslovakia. After World War II the company relocated to Nauheim, Germany, where it remains headquartered. The brand is known for producing professional saxophones with a distinctive tonal character often described as dark, warm, and harmonically rich — qualities that have earned it a following in jazz circles.

The company's flagship professional line is the SX90R series, developed in the late 1980s with input from jazz saxophonist Peter Ponzol, alongside the SX90 and CX90 professional models. Keilwerth also offers the ST series of student and intermediate saxophones and produces a full range from soprano through bass saxophone. The brand is particularly noted for its nickel-silver body variants and its straight-neck alto design.

Keilwerth has been endorsed by a range of prominent jazz saxophonists including Branford Marsalis, Ernie Watts, James Moody, Courtney Pine, Dave Liebman, Grover Washington Jr., and Kirk Whalum. The company is part of the Buffet Crampon group.

Keilwerth has 14 products cataloged on Equipboard, including Tenor Saxophones, Alto Saxophones, and Baritone & Bass Saxophones. Their gear is featured by 4 artists, with the strongest followings in Rock, Pop, and Electronic. Notable users include Clarence Clemons, Ian Kirkham, and i k y m.