New Jersey is a state located in both the Mid-Atlantic and Northeastern regions of the United States. Located at the geographic hub of the heavily urbanized Northeast megalopolis, it is bordered to the northwest, north, and northeast by New York State; on its east, southeast, and south by the Atlantic Ocean; on its west by the Delaware River and Pennsylvania; and on its southwest by Delaware Bay and Delaware. At 7,354 square miles (19,050 km²), New Jersey is the fifth-smallest state in land area. According to a 2024 U.S. Census Bureau estimate, it is the 11th-most populous state, with over 9.5 million residents, its highest estimated count ever. The state capital is Trenton, and the state's most populous city is Newark. New Jersey is the only U.S. state in which every county is deemed urban by the U.S. Census Bureau. It is the most densely populated U.S. state.

New Jersey was first inhabited by Paleo-Indians as early as 13,000 BC. The Lenape were the dominant Indigenous group when Europeans arrived in the early 17th century, and they were subdivided into dialectal groups such as the Munsee, in the north, and the Unami and the Unalachtigo, elsewhere. Dutch and Swedish colonists founded the first European settlements in the state, with the British later seizing control of the region and establishing the Province of New Jersey, named after Jersey. The colony's fertile lands and relative religious tolerance drew a large and diverse population. New Jersey was among the Thirteen Colonies that supported the American Revolution, hosting several pivotal battles and military commands in the American Revolutionary War. New Jersey remained in the Union during the American Civil War and provided troops, resources, and military leaders in support of the Union Army. After the war, the state emerged as a major manufacturing center and a leading destination for immigrants, helping drive the Industrial Revolution in the U.S. New Jersey was the site of many industrial, technological, and commercial innovations. Many prominent Americans associated with New Jersey have proven influential nationally and globally, including in academia, advocacy, business, entertainment, government, military, non-profit leadership, and other fields.

New Jersey's central location in the Northeast megalopolis helped fuel its rapid growth and suburbanization in the second half of the 20th century. Since the beginning of the 21st century, the state's economy has become highly diversified, with major sectors, including New Jersey's role as the world's largest pharmaceutical industry hub— as well as biotechnology, information technology, finance, digital media, filmmaking, and tourism, and it has become an Atlantic seaboard epicenter for logistics and distribution. New Jersey is a major destination for immigrants and is home to one of the world's most multicultural populations. Echoing historical trends, the state has increasingly re-urbanized, with growth in cities outpacing suburbs since 2008.

New Jersey is one of the most educated, affluent, healthy, diverse, and highly developed states in the U.S., ranking high among states in several quality of life metrics. New Jersey had a median household income of $99,781 as of 2023, the second-highest of any U.S. state behind Massachusetts. Almost one-tenth of all households in the state, or over 323,000, are millionaires, the highest representation of millionaires among all states. New Jersey's public school system consistently ranks at or among the top of all U.S. states. In 2024, New Jersey was ranked as having the second-healthiest population overall. New Jersey ranks near the top on both the American Human Development Index and the standard Human Development Index. According to climatology research by the U.S. National Oceanic and Atmospheric Administration, New Jersey has been the fastest-warming state by average air temperature over a 100-year period beginning in the early 20th century, which has been attributed to warming of the North Atlantic Ocean.

The pressure of collision between North America and Africa gave rise to the Appalachian Mountains. Around 18,000 years ago, the Ice Age resulted in glaciers that reached New Jersey. As glaciers retreated, they left behind Lake Passaic along with rivers, meadows, swamps, and gorges.

Since the 6th millennium BC, Native American people have inhabited New Jersey, beginning with the Lenape tribe. Scheyichbi is the Lenape name for the land that represents present-day New Jersey. The Lenape were several autonomous groups that practiced maize agriculture in order to supplement their hunting and gathering in the region surrounding the Delaware River, the lower Hudson River, and western Long Island Sound. The Lenape were divided into matrilineal clans that were based upon common female ancestors. Clans were organized into three distinct phratries identified by their animal sign: Turtle, Turkey, and Wolf. They first encountered the Dutch in the early 17th century, and their primary relationship with the Dutch and later European settlers was through fur trade.

The Dutch were the first Europeans to lay claim to geographic territory in New Jersey. The Dutch colony of New Netherland consisted of parts of the modern Mid-Atlantic states. Although the European principle of land ownership was not recognized by the Lenape, Dutch West India Company policy required its colonists to purchase land that they settled. The first to do so was Michiel Pauw, who established a patron ship called Pavonia in 1630 along North River, that eventually became Bergen. Peter Minuit's purchase of lands along the Delaware River established the colony of New Sweden, that lasted until the Dutch conquered it in 1655. Then the entire region became a territory of England on June 24, 1664, after an English fleet under command of Colonel Richard Nicolls sailed into what is now New York Harbor and took control of Fort Amsterdam, annexing the entire province.

During the English Civil War, the Channel Island of Jersey remained loyal to the British Crown and gave sanctuary to the King. In the Royal Square in St Helier, Charles II of England was proclaimed King in 1649, following the execution of his father, Charles I. North American lands were divided by Charles II, who gave his brother, the Duke of York (later King James II), the region between New England and Maryland as a proprietary colony (as opposed to a royal colony). James then granted land between the Hudson River and the Delaware River (the land that would become New Jersey) to two friends who had remained loyal through the English Civil War: Sir George Carteret and Lord Berkeley of Stratton. The area was named the Province of New Jersey.