Kailua is a census-designated place (CDP) in Hawaiʻi County, Hawaii, United States, in the North Kona District of the Island of Hawaiʻi. It is the center of commerce and of the tourist industry on West Hawaiʻi. Its post office is designated Kailua-Kona to differentiate it from the larger Kailua located on windward side of Oʻahu island, and it is sometimes referred to as Kona in everyday speech. The city is served by Kona International Airport, located just to the north in the adjacent Kalaoa CDP. Kailua-Kona was the closest major settlement to the epicenter of the 2006 Hawaiʻi Earthquake.

Oahu, known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the State of Hawaiʻi. The state capital Honolulu is located on the southeast coast. Including small close-in offshore islands such as Ford Island and the islands in Kaneohe Bay and off the eastern coast, it has a total land area of 596.7 square miles, making it the 20th largest island in the United States. In the greatest dimension, this volcanic island is 44 miles long and 30 miles across. The length of the shoreline is 227 miles. The island is the result of two separate shield volcanoes: Waiʻanae and Koʻolau, with a broad "valley" or saddle between them. The highest point is Mt. Ka'ala in the Waiʻanae Range, rising to 4,003 feet above sea level.