Mililani is a city located near the center of the island of Oʻahu in Honolulu County, Hawaiʻi, United States. It consists of two census-designated places, Mililani Town, with a population of 27,629 at the 2010 census, and Mililani Mauka, with a 2010 census population of 21,039.
Mililani sits on former plantation fields owned by Castle & Cooke, which began planning for its development in the early 1960s under its Oceanic Properties subsidiary. Castle & Cooke's plan was to collaborate with planners and architects on making Mililani Town a satellite city that would satisfy Oʻahu's pent-up demand for housing with a new affordable community. Architect and developer Al Boeke, who would later create the planned community of Sea Ranch, California, was the development director of Mililani. The first homes in Mililani went on sale on June 3, 1968.
In 1976, the Interstate H-2 opened, cutting travel time from Mililani to Honolulu in half. In 1986, Mililani was named an All-America City in recognition of a community effort to clean up drinking water contaminated with agricultural pesticides. It is the only community in Hawaiʻi ever to receive this distinction.
On April 6, 1990, ground was broken for Mililani Mauka, a newer and more upscale community east of the Interstate H-2. The first homeowners moved into Mauka in 1992.