Ulupō Heiau is an ancient Hawaiian ceremonial site at Kailua on Oʻahu, beside Kawai Nui Marsh, where rich fisheries, irrigated fields, and canoe landings helped make the area a center of power. Historically linked to Oʻahu’s ruling chiefs, including Kakuhihewa and Kualiʻi, it likely reached peak importance around 1750 before being abandoned after Oʻahu’s conquest in the 1780s. Its massive stone platform reflects major labor and chiefly authority. Probably first an agricultural heiau supported by nearby springs and pond resources, it may later have become a luakini heiau. Today its remains illuminate religion, agriculture, and political power in pre-contact Hawaiʻi.