The Northeastern United States (also referred to as the Northeast, the East Coast, or the American Northeast) is one of the four census regions defined by the United States Census Bureau. Located on the Atlantic coast of North America, the region borders Canada to its north, the Southern United States to its south, the Midwestern United States to its west, and the Atlantic Ocean to its east.

The Northeast is one of the four regions defined by the U.S. Census Bureau for the collection and analysis of statistics. The Census Bureau defines the region as including the six New England states of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont, and three lower North-Eastern states of New Jersey, New York, and Pennsylvania. Some expanded definitions of the region include Mid-Atlantic locations such as Delaware, Maryland, Northern Virginia, and Washington, D.C.

The region is the base for the Northeast megalopolis, which includes many of the nation's largest metropolitan areas, including Boston, New York City, and Philadelphia. The megalopolis makes up 67% of the region's total population of 57,609,148. The gross domestic product of the region was $5.1 trillion as of 2022 and contains some of the most developed states based on the Human Development Index, with every state above the national average. It is also the most densely populated region in the United States, with 320 people per square mile (120 people/km²). The U.S. Census Bureau defines the Northeast United States as having a total area of 181,324 sq mi (469,630 km²), making it the smallest region of the United States by total area.

Anthropologists recognize the "Northeastern Woodlands" as one of the cultural regions that existed in the Western Hemisphere at the time of European colonists in the 15th and later centuries. Most did not settle in North America until the 17th century. The cultural area, known as the "Northeastern Woodlands", in addition to covering the entire Northeast U.S., also covered much of what is now Canada and other regions of what is now the eastern United States.

Among the many tribes inhabiting this area were those that made up the Iroquois nations and the numerous Algonquian peoples. In the United States of the 21st century, 18 federally recognized tribes reside in the Northeast. For the most part, the people of the Northeastern Woodlands, on whose lands European fishermen began camping to dry their codfish in the early 1600s, lived in villages, especially after being influenced by agricultural traditions of the Ohio and Mississippi valley societies.

All of the U.S. states making up the Northeastern region were among the original Thirteen Colonies, though Maine and Vermont were part of other colonies before the United States became independent in the American Revolution. The two cultural and geographic regions that form parts of the Northeastern region have distinct histories. The first European explorer known to have explored the Atlantic shoreline of the Northeast since the Norse was Giovanni da Verrazzano in 1524. His ship La Dauphine explored the coast from what is now known as Florida to New Brunswick.

The first Europeans to settle and colonize New England were Pilgrims from England, who landed in present-day Massachusetts in 1620. The Pilgrims arrived on the ship Mayflower and founded Plymouth Colony so they could practice religion freely. Ten years later, a larger group of Puritans settled north of Plymouth Colony in Boston to form Massachusetts Bay Colony. In 1636, colonists established Connecticut Colony and Providence Plantations.

Providence was founded by Roger Williams, who was banished by Massachusetts for his beliefs in freedom of religion, and it was the first colony to guarantee all citizens freedom of worship. Anne Hutchinson, who was also banished by Massachusetts, formed the town of Portsmouth. Providence, Portsmouth and two other towns (Newport and Warwick) consolidated to form the Colony of Rhode Island and Providence Plantations.