The King of Jazz refers to Paul Whiteman, an influential American bandleader and orchestral director known for popularizing jazz music during the 1920s. His blend of classical music with jazz elements helped shape the sound of the era, making him a significant figure in the evolution of jazz as a mainstream genre. Whiteman's innovative approach included arranging jazz for larger orchestras, which contributed to the rise of big band music and broadened jazz's appeal to a wider audience.