The East Coast of the United States, also known as the Eastern Seaboard, the Atlantic Coast, and the Atlantic Seaboard, is the coastline along which the Eastern United States meets the North Atlantic Ocean. The coastal states that have shoreline on the Atlantic Ocean are, from north to south, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida.^[2]

The place name "East Coast" derives from the idea that the contiguous 48 states are defined by two major coastlines, one at the western edge and one on the eastern edge. Other terms for referring to this area include the "Eastern Seaboard" ("seaboard" being American English for coast), "Atlantic Coast", and "Atlantic Seaboard" (because the coastline lies along the Atlantic Ocean).

The fourteen states that have a shoreline on the Atlantic Ocean are, from north to south, the U.S. states of Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida.^[2] In addition, Pennsylvania and the District of Columbia border tidal arms of the Atlantic (the Delaware River and the Potomac River, respectively). The states of Alabama, Mississippi, Louisiana, and Texas, (via the Gulf of Mexico) as well as the territories of Puerto Rico, the US Virgin Islands, and Navassa Island (the latter only bordering the Caribbean Sea) have Atlantic coastline, but are not included in the definition.

Although Vermont and West Virginia have no Atlantic coastline, they are sometimes grouped with the Eastern Seaboard states because of their locations in New England and the Old South,^[3] and their history as part of the land base of the original Thirteen Colonies (viz. the Colony of New Hampshire, the Colony of New York and the Colony of Virginia).

The original thirteen colonies of Great Britain in North America all lay along the East Coast.^[1]

Two additional U.S. states on the East Coast were not among the original thirteen colonies: Maine (became part of the English colony of Massachusetts in 1677)^[4] and Florida (part of New Spain until 1821, though held by the British from after the end of the French and Indian War until 1781).^[5]

The Middle Colonies (New Jersey, Pennsylvania, New York, and Delaware) had been owned by the Dutch as New Netherland, until they were captured by the English in the mid-to-late 17th century.

There are three basic climate regions on the East Coast according to the Köppen climate classification from north to south based on the monthly mean temperature of the coldest month (January):

The region from northern Maine south to northern Rhode Island and Connecticut has a continental climate, with warm summers, and cold and snowy winters. The area from southern Rhode Island, Connecticut and New York City south to central Florida has a temperate climate, with long, hot summers and cold winters with occasional snow in the northern portions, and milder winters in the southern portions. Around south-central Florida southward (Stuart, south through the Florida Keys) has a tropical climate, which is frost free and is warm to hot all year.

Average monthly precipitation ranges from a slight late fall (November) maximum from Massachusetts northward (as at Portland, Maine), to a slight summer maximum in the Mid-Atlantic states from southern Connecticut south to Virginia (as at Wilmington, Delaware, and Norfolk, Virginia), to a more pronounced summer maximum from Cape Hatteras, North Carolina, southward along the Southeastern United States coast to Savannah, Georgia. The Florida peninsula has a sharp wet-summer/dry-winter pattern, with 60 to 70 percent of precipitation falling between June and October in an average year, and a dry, and sunny late fall, winter, and early spring.

Although landfalls are rare, the Eastern seaboard is susceptible to hurricanes in the Atlantic hurricane season, officially running from June 1 to November 30, although hurricanes can occur before or after these dates.^[6] Hurricanes Hazel, Hugo, Bob, Isabel, Irene, Sandy, and most recently Florence are some of the more significant storms to have affected the region.

The East Coast is a low-relief, passive margin coast.^[7] It has been shaped by the Pleistocene glaciation in the far northern areas from New York City northward, with offshore islands such as Nantucket, Block Island, Fishers Island, the nearly peninsular Long Island and New York City's Staten Island the result of terminal moraines, with Massachusetts' unique peninsula of Cape Cod showing the additional action of outwash plains, besides terminal moraines. The coastal plain broadens southwards, separated from the Piedmont region by the Atlantic Seaboard fall line of the East Coast rivers, often marking the head of navigation and prominent sites of cities. The coastal areas from Long Island south to Florida are often made up of barrier islands that front the coastal areas, with the long stretches of sandy beaches. Many of the larger capes along the lower East Coast are in fact barrier islands, like the Outer Banks of North Carolina and Cape Canaveral, Florida. The Florida Keys are made up of limestone coral and provide the only coral reefs on the US mainland.

In 2010, the population of the states which have shoreline on the East Coast was estimated at 112,642,503 (36% of the country's total population). The East Coast is the most populated coastal area in the United States.^[8]

The primary Interstate Highway along the East Coast is Interstate 95, completed in 2018,^[9][10] which replaced the historic U.S. Route 1 (Atlantic Highway), the original federal highway that traversed all East Coast states, except Delaware.^[11] By water, the East Coast is connected from Boston, Massachusetts to Miami, Florida, by the Intracoastal Waterway, also known as the East Coast Canal, which was completed in 1912.^[12][13] Amtrak's Downeaster and Northeast Regional offer the main passenger rail service on the Seaboard. The Acela Express offers the only high-speed rail passenger service in the Americas. Between New York and Boston the Acela Express has up to a 54% share of the combined train and air passenger market.^[14][15]

Some of the largest airports in the United States are located in states which lie in the East Coast of the United States, such as John F. Kennedy International Airport in New York, Logan International Airport in Boston, Newark Liberty Airport in Newark, New Jersey, Philadelphia International Airport in Philadelphia, Baltimore–Washington International Airport near Baltimore, Washington-Dulles International Airport near Washington, D.C., Hartsfield International Airport in Atlanta, Miami International Airport in Miami, Charlotte Douglas International Airport in Charlotte, North Carolina, Tampa International Airport in Tampa and Orlando International Airport in Orlando, Florida.