Hawaiʻi, also called the Island of Hawaiʻi,the Big Island or Hawaiʻi Island, which comprises Hawaiʻi County and the Hilo, HI Micropolitan Statistical Area, is an island, county, and Micropolitan Statistical Area located in the U.S. state of Hawaii in the Hawaiian Islands. It is the largest and the southeastern-most of the Hawaiian islands, a chain of volcanic islands in the North Pacific Ocean. With an area of 4,028 square miles (10,430 km2), it is larger than all of the other islands in the archipelago combined and is the largest island in the United States. The island is often referred to as the "Big Island" to reduce confusion between the island and the state.

As of the 2010 Census the population was 185,079. The county seat and largest city is Hilo. There are no incorporated cities in Hawaiʻi County (see Hawaii Counties). Hawaiʻi County has a mayor-council form of government.

Hawaii County is one of seven counties in the United States to share the same name as the state in which it is located (the other six counties are Arkansas County, Idaho County, Iowa County, New York County, Oklahoma County, and Utah County).