Hilo (; Hawaiian pronunciation: [ˈhilo]) is the largest town and census-designated place (CDP) in Hawaii County, Hawaii, United States, which encompasses the Island of Hawaiʻi. The population was 43,263 according to the 2010 census.
Hilo is the county seat of the County of Hawaiʻi and is in the District of South Hilo. The town overlooks Hilo Bay, at the base of two shield volcanoes, Mauna Loa, an active volcano, and Mauna Kea, a dormant volcano. Mauna Kea is the site of some of the world's most important ground-based astronomical observatories. Much of the city is at risk from lava flows from Mauna Loa, and the bayfront was twice destroyed by tsunamis. The majority of human settlement in Hilo stretches from Hilo Bay to Waiākea-Uka, on the flanks of the volcanoes.
Hilo is home to the University of Hawaiʻi at Hilo, ʻImiloa Astronomy Center of Hawaiʻi, as well as the Merrie Monarch Festival, a week-long celebration of ancient and modern hula that takes place annually after Easter. Hilo is also home to the Mauna Loa Macadamia Nut Corporation, one of the world's leading producers of macadamia nuts. The town is served by Hilo International Airport.
Around 1100 AD, the first Hilo inhabitants arrived, bringing with them Polynesian knowledge and traditions. Although archaeological evidence is scant, oral history has many references to people living in Hilo, along the Wailuku and Wailoa rivers during the time of ancient Hawaii.