Kailua (käēlōˈə) [key], uninc. city (1990 pop. 36,818), Honolulu co., Hawaii, on the southeastern coast of Oahu, on Kailua Bay. A Univ. of Hawaii agricultural experiment station is in Kailua and a U.S. marine corps air facility is nearby. Many ancient temple ruins, including Ulu Po Heiau State Monument, are in the area.