Native Americans (also called American Indians, First Americans, or Indigenous Americans) are the Indigenous peoples of the United States, particularly of the lower 48 states and Alaska. They may also include any Americans whose origins lie in any of the indigenous peoples of North or South America. The United States Census Bureau publishes data about "American Indians and Alaska Natives", whom it defines as anyone "having origins in any of the original peoples of North and South America ... and who maintains tribal affiliation or community attachment". The census does not, however, enumerate "Native Americans" as such, noting that the latter term can encompass a broader set of groups, e.g. Native Hawaiians, which it tabulates separately.

The European colonization of the Americas from 1492 resulted in a precipitous decline in the size of the Native American population because of newly introduced diseases, including weaponized diseases and biological warfare by colonizers, wars, ethnic cleansing, and enslavement. Numerous scholars have classified elements of the colonization process as comprising genocide against Native Americans. As part of a policy of settler colonialism, European settlers continued to wage war and perpetrated massacres against Native American peoples, removed them from their ancestral lands, and subjected them to one-sided government treaties and discriminatory government policies. Into the 20th century, these policies focused on forced assimilation.

When the United States was established, Native American tribes were considered semi-independent nations, because they generally lived in communities which were separate from communities of white settlers. The federal government signed treaties at a government-to-government level until the Indian Appropriations Act of 1871 ended recognition of independent Native nations, and started treating them as "domestic dependent nations" subject to applicable federal laws. This law did preserve rights and privileges, including a large degree of tribal sovereignty. For this reason, many Native American reservations are still independent of state law and the actions of tribal citizens on these reservations are subject only to tribal courts and federal law. The Indian Citizenship Act of 1924 granted US citizenship to all Native Americans born in the US who had not yet obtained it. This emptied the "Indians not taxed" category established by the United States Constitution, allowed Natives to vote in elections, and extended the Fourteenth Amendment protections granted to people "subject to the jurisdiction" of the United States. However, some states continued to deny Native Americans voting rights for decades. Titles II through VII of the Civil Rights Act of 1968 comprise the Indian Civil Rights Act, which applies to Native American tribes and makes many but not all of the guarantees of the U.S. Bill of Rights applicable within the tribes.

Since the 1960s, Native American self-determination movements have resulted in positive changes to the lives of many Native Americans, though there are still many contemporary issues faced by them. Today, there are over five million Native Americans in the US, about 80% of whom live outside reservations. As of 2020, the states with the highest percentage of Native Americans are Alaska, Oklahoma, Arizona, California, New Mexico, and Texas.

The history of Native Americans in the United States began tens of thousands of years ago with the settlement of the Americas by the Paleo-Indians. The Eurasian migration to the Americas occurred over millennia via Beringia, a land bridge between Siberia and Alaska, as early humans spread southward and eastward. Archaeological evidence suggests these migrations began 25,000 years ago and continued until around 12,000 years ago. Some may have arrived even earlier, fishing in kayaks along what is known as the "Kelp Highway". Major Paleo-Indian cultures included the Clovis and Folsom traditions, identified through unique spear points and large-game hunting methods.

Around 8000 BCE, as the climate stabilized, new cultural periods like the Archaic stage arose, during which hunter-gatherer communities developed complex societies. The Mound Builders created large earthworks, such as at Watson Brake and Poverty Point, which date to 3500 BCE and 2200 BCE. By 1000 BCE, Native societies in the Woodland period developed advanced social structures and trade networks, with the Hopewell tradition connecting the Eastern Woodlands to the Great Lakes and the Gulf of Mexico. This period led to the Mississippian culture, with large urban centers like Cahokia—a city with complex mounds and a population exceeding 20,000 by 1250 CE.

Ethnographers classify the Indigenous peoples of North America into ten cultural areas inhabited by groups who share certain cultural traits:^{[citation needed]} the Arctic, Subarctic, Northeastern Woodlands, Southeastern Woodlands, Great Plains, Great Basin, Northwest Plateau, Northwest Coast, California, and Southwest (Oasisamerica). At the time of the first contact, Indigenous cultures varied widely, with some Northeastern and Southwestern groups being matrilineal and organized on collective bases unfamiliar to Europeans. Land was typically held communally, in contrast to European property rights traditions. These differences, compounded by shifting alliances and warfare, generated political tension, ethnic violence, and disruption.^{[citation needed]}

Beginning near the end of the 15th century, migration of Europeans to the Americas led to centuries of population, cultural, and agricultural transfer between Old and New World societies, known as the Columbian exchange. Because most Native groups preserved their histories by means of oral traditions and artwork, the first written accounts of contact were provided by Europeans.