Native Americans, also known as First Americans, Indigenous Americans, American Indians, and other terms, are the Indigenous peoples of the United States, including Hawaii and territories of the United States, and other times limited to the mainland. There are 574 federally recognized tribes living within the US, about half of which are associated with Indian reservations. "Native Americans" (as defined by the United States Census) are Indigenous tribes that are originally from the contiguous United States, along with Alaska Natives.

Indigenous peoples of the United States who are not American Indian or Alaska Native include Native Hawaiians, Samoans, and Chamorros. The US Census groups these peoples as "Native Hawaiian and other Pacific Islander".

The ancestors of living Native Americans arrived in what is now the United States at least 15,000 years ago, possibly much earlier, from Asia via Beringia. A vast variety of peoples, societies and cultures subsequently developed. European colonization of the Americas, which began in 1492, resulted in a precipitous decline in Native American population because of new diseases, wars, ethnic cleansing, and enslavement. After its formation, the United States, as part of its policy of settler colonialism, continued to wage war and perpetrated massacres against many Native American peoples, removed them from their ancestral lands, and subjected them to one-sided treaties and to discriminatory government policies, later focused on forced assimilation, into the 20th century. 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 United States, 78% of whom live outside reservations: California, Arizona and Oklahoma have the largest populations of Native Americans in the United States. Most Native Americans live in small towns or rural areas.

When the United States was created, established Native American tribes were generally considered semi-independent nations, as they generally lived in communities separate from 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 the rights and privileges agreed to under the treaties, 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, often differently applicable to tribal lands than to U.S. state or territory by exemption, exclusion, treaty, or superseding tribal or federal law.

The Indian Citizenship Act of 1924 granted U.S. citizenship to all Native Americans born in the United States who had not yet obtained it. This emptied the "Indians not taxed" category established by the United States Constitution, allowed natives to vote in state and federal 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 several decades. Titles II through VII of the Civil Rights Act of 1968 comprise the Indian Civil Rights Act, which applies to the Native American tribes of the United States and makes many but not all of the guarantees of the U.S. Bill of Rights applicable within the tribes (that Act appears today in Title 25, sections 1301 to 1303 of the United States Code).

Ishi (c. 1861 – March 25, 1916) was the last known member of the Native American Yahi people from the present-day state of California in the United States. The rest of the Yahi (as well as many members of their parent tribe, the Yana) were killed in the California genocide in the 19th century. Ishi, who was widely acclaimed as the "last wild Indian" in the United States, lived most of his life isolated from modern American culture. In 1911, aged 50, he emerged at a barn and corral, 2 mi (3.2 km) from downtown Oroville, California.

Ishi, which means "man" in the Yana language, is an adopted name. The anthropologist Alfred Kroeber gave him this name because in the Yahi culture, tradition demanded that he not speak his own name until formally introduced by another Yahi. When asked his name, he said: "I have none, because there were no people to name me," meaning that there was no other Yahi to speak his name on his behalf.

Ishi was taken in by anthropologists at the University of California, Berkeley, who both studied him and hired him as a janitor. He lived most of his remaining five years in a university building in San Francisco. His life was depicted and discussed in multiple films and books, notably the biographical account Ishi in Two Worlds published by Theodora Kroeber in 1961.