Oahu is one of the eight main islands of the Hawaii archipelago and home to the capital of the US state of Hawaii: Honolulu. Oahu is also called The Gathering Place.
With 1,557 km², Oahu is the third-largest island in the archipelago. Nearly one million people live on Oahu, making up around 75 percent of the entire state's population.
Oahu is 64 km long and 42 km wide and is the economic center of Hawaii.
Oahu was formed by two volcanoes, Wai'anae and Ko'olau, connected by a wide saddle.
The highest point is Mount Ka'ala at 1,220 meters. The longest river on the island is the Anahulu River.

Honolulu ("protected bay") with 3,700 residents stretches across a large part of southeastern Oahu and is home to Hawaii's largest seaport. The metropolis has a distinctly American feel with its skyscrapers.
The ten-story Aloha Tower has been the landmark of Honolulu Harbor since 1921.
Other well-known places on O'ahu include Waikīkī, Pearl Harbor, Diamond Head, Hanauma Bay, Kāne'ohe Bay, Kailua Bay, and the North Shore.

Pearl Harbor is the submarine base, naval fleet headquarters, and military command center for the entire Pacific region. The naval base became world-famous on December 7, 1941, when Japan launched a surprise attack on the Americans stationed there. In the early morning hours, 2,403 US citizens were killed and the naval base was completely destroyed. The United States subsequently entered World War II.
The USS Arizona, which sank during the attack along with its crew, was never salvaged and rests today as a memorial on the floor of Pearl Harbor. A floating memorial, the USS Arizona Memorial, was anchored above the wreck. The names of the victims are engraved on the 56-meter-long monument. The oil that still seeps from the wreck and can be seen on the water's surface is known as the "Tears of the Arizona." Close to the Arizona Memorial, the museum ship USS Missouri has been on display since 1998 — the battleship on which Japan's unconditional surrender was signed on September 2, 1945, in Tokyo Bay.
Today, approximately 40,000 soldiers are stationed at Pearl Harbor.

The many popular beaches attract tourists from all over the world. Above all, the beach of Waikīkī — also known as the "Metropolis of the South Seas" — with the extinct volcanoes Diamond Head and Punchbowl Crater rising behind it, is one of the most popular on the island. The Waikīkī district alone has around 38,000 hotel rooms.
The beaches on the west coast around Pūpūkea offer the best surfing conditions in the world, and the most important competitions are held here.

Some of the most famous surf beaches are Sunset Beach, Himalaya's, Holton's, Rocky Point, Alligator Rock, and of course the Banzai Pipeline at Ehukai Beach Park.
The Waimea Falls Park, a botanical garden in the Waimea Stream valley, is a wonderful sight.
Just off the eastern coast of Oahu lie numerous small islets (Mānana, Mokoliʻi, Moku Manu, Nā Mokulua) that belong to the Hawaii State Seabird Sanctuary and may not be entered, or only under special conditions.