William Pitt Leleiohoku II, born Kalahoʻolewa (January 10, 1855 – April 9, 1877), was a prince of the Kingdom of Hawaiʻi and member of the reigning House of Kalākaua. At birth, he was hānai (informally adopted) by Ruth Keʻelikōlani and later legally adopted by her in 1862 as the heir to her vast land holdings. He was educated at St. Alban's College, a precursor of the present ʻIolani School. After finishing his education, he worked in the governmental Foreign Office and served as an officer on the personal military staff of King Lunalilo. On February 14, 1874, his brother Kalākaua was elected king after the death of Lunalilo. Declared heir apparent to his childless brother, Leleiohoku was expected to inherit the throne of Hawaii. He would also serve as a Privy Councilor and member of the House of Nobles in the Legislature of the Kingdom of Hawaii. During Kalākaua's trip to the United States to negotiate the Reciprocity Treaty of 1875, he ruled as regent in the monarch's absence from November 17, 1874, to February 15, 1875. Leleiohoku died at the age of 22 from rheumatic fever resulting in the proclamation of his sister Liliʻuokalani as the next heir to the throne. An accomplished musical composer, Leleiohoku is remembered for composing many folk songs including "Kāua I Ka Huahuaʻi", which was adapted into the American popular song "Hawaiian War Chant".