Prince William Pitt Leleiohoku II, born Kalahoʻolewa on January 10, 1855, in Honolulu, was a notable figure in the Hawaiian Kingdom as a prince and member of the House of Kalākaua. He was informally adopted at birth by Ruth Keʻelikōlani and later legally adopted in 1862, becoming heir to her extensive land holdings. Educated at St. Alban's College, Leleiohoku went on to work in the governmental Foreign Office and served as an officer on King Lunalilo's personal military staff. Following the election of his brother Kalākaua as king in 1874, Leleiohoku was declared heir apparent to the throne. He served as a Privy Councilor and member of the House of Nobles and ruled as regent during Kalākaua's absence from November 17, 1874, to February 15, 1875.

Leleiohoku was also a celebrated composer, contributing significantly to the musical revival in Hawaii during the late 19th century. He founded the Kawaihau Singing Club and was known for his exceptional voice and talent in composition, which was praised by his sister Queen Liliʻuokalani. His compositions often adapted folk tunes from various cultures, and he is remembered for songs like "Kāua I Ka Huahuaʻi," which later became known as "Hawaiian War Chant."

Leleiohoku died at the young age of 22 on April 9, 1877, from rheumatic fever, leading to his sister Liliʻuokalani being named the next heir to the throne. He and his siblings, known as Na Lani ʻEhā ("The Royal Four"), are honored by the Hawaiian Music Hall of Fame for their contributions to Hawaii's musical heritage.