Lunalilo, born William Charles Lunalilo (January 31, 1835 – February 3, 1874), was king of the Kingdom of Hawaiʻi from January 8, 1873 until February 3, 1874. He was the most liberal king in Hawaiian history, but was the shortest-reigning monarch.

William Charles Lunalilo was born on January 31, 1835 in an area known as Pohukaina, now part of Honolulu. His mother was High Chiefess Miriam Auhea Kekāuluohi (later styled Kaʻahumanu III) and his father was High Chief Charles Kanaʻina. He was grandnephew of Kamehameha I. He was second cousin to King Kamehameha V, King Kamehameha IV, and Princess Victoria Kamāmalu through his mother, who was the cousin of Elizabeth Kīnaʻu (later called Kaʻahumanu II). His name translates as Luna (high) lilo (lost) or "so high up as to be lost to sight" in the Hawaiian language. He was also named after King William IV of Great Britain, a great friend of Hawaiian royalty.

He was declared eligible to succeed by the royal decree of King Kamehameha III and sent to the Chief's Children's School (later called the Royal School) when it was founded by missionaries Amos Starr Cooke and Juliette Montague Cooke. He learn to speak both Hawaiian and English; in fact, he is considered to have had the best mastery of English literature among all the Hawaiian monarchs.