Real name: William Kuali'i Sumner Ellis

William S. Ellis was an orchestra leader, singer, and composer from Honolulu, Hawaii (born January 18, 1874).

Trained on the piano since age 8, William Ellis played saxophone and stringed instruments with the Royal Hawaiian Band. He also directed the Royal Hawaiian Band's Glee Club. In 1899, Ellis brought a group of five other Hawaiian musicians to San Francisco where they recorded several cylinders for Edison Records, which probably were the first recordings of Hawaiian music. Only one of these still survives today. In July 1904, William and his younger brother, John S. Ellis (1877-1914), recorded 34 songs that were released on the Victor label under the name William S. Ellis and Ellis Bros. Glee Club or Ellis Brothers Glee Club Quartet.

Best-known among his compositions is the "Ellis March."