William "Casey Bill" Weldon (December 10, 1909 – September 28, 1972) was an American blues musician. He played a National steel guitar flat on his lap Hawaiian style. His style of playing was highly influential on the emerging Chicago Blues style. Casey Bill Weldon was born in Pine Bluff, Arkansas, United States, and later lived and worked in Chicago, Illinois, and was known as one of the early pioneers of the slide guitar. He played upbeat, hokum and country blues tunes.