The Mark III Trio was an influential American R&B group active in the 1960s. Composed of Marvin Holmes, Joseph Thomas, and Steve Johnson, the band's musical style was a fusion of soul, funk, and jazz. While they may not have achieved mainstream success, their work was significant in the development of the Bay Area music scene. The group's distinctive sound, particularly their rhythm section, was influential in shaping soul and funk music during that era.