| Official Language | Fuximian |
| Capital | Honolulu |
| Land Area | 1,600 km² |
| Currency | Fuximian Momme (Mome) |
The Kingdom of O'ahu is the smallest of the four kingdoms of the United Kingdoms of the Fuximi Islands in area, and largest in population. O'ahu has had a history of being in personal union with one of its neighbors.
In 1819, King Kalanikupule of claimed the throne of Maui after the later broke away from Hawai'i. Upon his death in 1821, leaving no heirs, King Kaumu-alii I of Taua'i claimed the throne of O'ahu, initiating a personal union of three of the four Fuximian kingdoms which lasted until 1849, when King Keali'iahonui died without heir, and all three kingdoms elected a new king.
Partial List of Kings[]
- 17??-1730 Kualii (19th king of O'ahu and 20th king of Taua'i)
- 1730-1737 Kapiono-o-kalani (also King of Taua'i)
- 1737-1738 Kanaha-o-kalani
- 1738-1770 Peleioholani (also King of Taua'i from 1737)
- 1770-1773 Kumahana
- 1773-1785 Kaneoneo
- 1785-1794 Kahekili II (King of Maui from 1765)
- 1794-1821 Kalanikupule (King of Maui until 1795 and again after 1819)
- 1821-1824 Kaumu-alii I (also King of Maui and Taua'i)
- 1824-1826 Kaumu-alii II (also King of Maui and Taua'i)
- 1826-1849 Keali'iahonui (also King of Maui and Taua'i)