Oahu or Oahu ( in Hawaiian), known as "The Gathering Place", is the third largest of the Hawaiian Islands and the most populous of the islands in the U.S. state of Hawaii. The state capital, Honolulu, is on Oahu's southeast coast. Including small close-in offshore islands such as Ford Island and the islands in Kaneohe Bay and off the eastern (windward) coast, it has a total land area of , making it the 20th largest island in the United States. In the greatest dimension, this volcanic island is long and across. The length of the shoreline is . The island is the result of two separate shield volcanoes: Waianae and Koolau, with a broad "valley" or saddle (the central Oahu Plain) between them. The highest point is Mt. Ka'ala in the Waianae Range, rising to above sea level.

O’ahu est la troisième île par la taille de l’archipel d'Hawaii et la plus peuplée des îles formant l’État de Hawaii. Elle couvre un total de 1 545,34 km², en incluant l’île de Ford et les îlots de la baie de Kaneohe et de la côte est. Elle a 366 kilomètres de côtes.

Oahu är den tredje största (1 600 km²) och den mest befolkade ön i ögruppen och delstaten Hawaii. Befolkningen uppgår till ca 900 000 vilket är ca 70% av den totala befolkningen i delstaten Hawaii.

Oahu (haw. Oʻahu) - wyspa pochodzenia wulkanicznego na Oceanie Spokojnym, w archipelagu Hawajów (USA).

L'isola di Oahu (in hawaiiano O'ahu) è l'isola delle Hawaii su cui si trovano la capitale, Honolulu, Pearl Harbor, e più della metà della popolazione dello stato - circa 900 mila abitanti.