Ohio is a Midwestern state of the United States. Part of the Great Lakes region, Ohio has long been a cultural and geographical crossroads in North America. At the time of European contact and in the years that followed, Native Americans in today's Ohio included the Shawnee, Iroquois, Miamis, and Wyandots. Beginning in the 1700s, the area was settled by people from New England, the Mid-Atlantic States, Appalachia, and the Upper South.

Prior to 1984, the United States Census Bureau considered Ohio part of the North Central Region. That region was renamed "Midwest" and split into two divisions. Ohio is now in the East North Central States division. Ohio has the highest population density of any state not on the Eastern Seaboard, and it is the seventh-largest state by population in the U.S.

Ohio was the first state admitted to the Union under the Northwest Ordinance. Its U.S. postal abbreviation is OH; its old-style abbreviation was O. Natives of Ohio are known as Ohioans or Buckeyes.