Steve Klein is a master luthier based in Sonoma, California, known for radical departures from traditional acoustic and electric guitar design. He built his first guitar in 1966 and emerged on the scene in 1967 with an ambitious reimagining of the steel string acoustic, drawing on bracing concepts developed by Dr. Michael Kasha and classical luthier Richard Schneider. His acoustic work is best represented by the large-bodied L-45.7, named for the 45.7 centimeter width of its lower bout, which uses long, thin tone bars, architectural flying braces, and a modified X brace pattern.

On the electric side, Klein developed a distinctive ergonomic, sculptural body shape in collaboration with Ronnie Montrose in the mid-1980s, debuting the design at a trade show in 1989 and spawning Klein Electric Division. His catalog includes the ergonomic s-Tele and SMK (an S-style design), as well as acoustic and electric basses and one-off special projects. Luthier Steven Kauffman has been a longtime collaborator, building roughly a hundred Klein acoustics through the Klein/Kauffman partnership.

Klein guitars have been played by Joni Mitchell, Bill Frisell, Michael Hedges, Andy Summers, Lou Reed, Steve Miller, and Joe Walsh, among others. His life and work are documented in Paul William Schmidt's book Art That Sings: The Life and Times of Luthier Steve Klein.

Steve Klein has 2 products cataloged on Equipboard, including Solid Body Electric Guitars. Their gear is featured by 7 artists, with the strongest followings in Rock, Jazz, and Folk, World, & Country. Notable users include Lou Reed, Andy Summers, and Bill Frisell.