Kaoru Ishikawa is the quality-management theorist closely associated with quality circles and fishbone diagrams.
Ishikawa was a Japanese organizational theorist and professor who helped develop Japan’s postwar quality movement. He promoted quality circles—small groups of employees who meet regularly to identify workplace problems, analyze causes, and suggest improvements. The approach brought frontline workers into quality management rather than leaving inspection solely to specialists or executives.
The fishbone diagram, formally called an Ishikawa or cause-and-effect diagram, organizes possible causes of a problem into branches leading to a stated effect. Its shape resembles a fish skeleton, which explains the popular name. Teams often use it during brainstorming and root-cause analysis, sometimes alongside the “5 Whys” technique.
Ishikawa drew on ideas associated with W. Edwards Deming and Joseph Juran, so those names can cause confusion. Deming is strongly linked with statistical quality control and management principles, while Juran is associated with the quality trilogy. The single answer tying both quality circles and fishbone diagrams together is Ishikawa.