New Jersey is a state in the Mid-Atlantic region of the Northeastern United States. It is a peninsula, bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware River and Pennsylvania; and on the southwest by the Delaware Bay and Delaware. New Jersey is the fourth-smallest state by area but the 11th-most populous, with 9 million residents as of 2017, and the most densely populated of the 50 U.S. states. New Jersey lies completely within the combined statistical areas of New York City and Philadelphia and is the third-wealthiest state by median household income as of 2016.

New Jersey was inhabited by Native Americans for more than 2,800 years, with historical tribes such as the Lenape along the coast. In the early 17th century, the Dutch and the Swedes made the first European settlements in the state. The English later seized control of the region, naming it the Province of New Jersey after the largest of the Channel Islands, Jersey, and granting it as a colony to Sir George Carteret and John Berkeley, 1st Baron Berkeley of Stratton. New Jersey was the site of several decisive battles during the American Revolutionary War in the 18th century.

In the 19th century, factories in cities (known as the "Big Six"), Camden, Paterson, Newark, Trenton, Jersey City, and Elizabeth helped to drive the Industrial Revolution. New Jersey's geographic location at the center of the Northeast megalopolis, between Boston and New York City to the northeast, and Philadelphia, Baltimore, and Washington, D.C., to the southwest, fueled its rapid growth through the process of suburbanization in the second half of the 20th century. In the first decades of the 21st century, this suburbanization began reverting with the consolidation of New Jersey's culturally diverse populace toward more urban settings within the state, with towns home to commuter rail stations outpacing the population growth of more automobile-oriented suburbs since 2008.