Diamond Head is a volcanic tuff cone located on the island of Oahu in the state of Hawaii. It is one of the most iconic landmarks in Hawaii and is a popular tourist destination. The cone was formed approximately 300,000 years ago during a series of volcanic eruptions.

Diamond Head gets its name from the 19th-century British sailors who mistakenly believed that the calcite crystals found on the slopes of the crater were diamonds. The cone is also known by its Hawaiian name, Lēʻahi.

Diamond Head is a popular hiking destination, and the trail to the summit offers stunning views of the surrounding coastline and the city of Honolulu. The trail is approximately 1.6 miles round trip and can be steep and strenuous in some areas. At the summit, visitors can see bunkers and observation stations that were used during World War II.

In addition to hiking, Diamond Head is also home to several military installations, including Fort Ruger, the oldest military reservation in Hawaii.