Sigma Guitars traces its origins to 1970, when C.F. Martin & Company launched the brand as an affordable alternative to its own premium acoustic instruments. Faced with growing competition from Japanese-made guitars, Martin commissioned specially trained workers in Japanese factories to build Sigma guitars to American quality standards, with each instrument inspected in the United States before sale. The strategy proved successful, and Sigma quickly earned a reputation for delivering Martin-inspired tone and craftsmanship at a fraction of the price. Production moved from Japan (1970–1983) to Korea (1984–1994), then Taiwan, and later Indonesia before Martin discontinued the line in 2007.

In 2011, German company AMI Musical Instruments GmbH acquired the international rights to the Sigma name and relaunched the brand under the guidance of luthier Günther Lutz, who brought over 40 years of acoustic guitar expertise to the revival. The relaunched lineup includes dreadnought, 000, OM, and travel-size acoustics, as well as classical guitars, acoustic basses, ukuleles, and semi-hollow electric guitars. Popular models include the DM and DR dreadnought series, the 000ME+, and the all-solid-wood SG series. All Sigma guitars feature solid tops as a baseline, with higher-tier models using all-solid tonewoods.

Sigma occupies a well-regarded niche in the affordable-to-mid-range acoustic guitar market, offering instruments with classic Martin-influenced body shapes and bracing patterns. The brand has a dedicated following among players and collectors, particularly for the sought-after Japanese-made vintage models from the 1970s and early 1980s.

Sigma has 146 products cataloged on Equipboard, including Acoustic-Electric Guitars, Steel-string Acoustic Guitars, and Camera Lenses. Their gear is featured by 34 artists, with the strongest followings in Rock, Pop, and Stage & Screen. Notable users include North Borders, Isaac Wood, and Georgia Ellery. Most Sigma products fall in the mid-tier range — professional-grade without flagship pricing.