Immigration is the process through which individuals become permanent residents or citizens of another country. It involves moving to a new country or region with the intention of staying and living there. People may choose to immigrate for a variety of reasons, such as employment opportunities, to escape a violent conflict, environmental factors, educational purposes, or to reunite with family. Immigration can be voluntary or involuntary.

In the United States, immigration is an area of federal oversight, although some states have passed laws intended to bolster the enforcement of existing federal immigration laws. The body of law governing U.S. immigration policy is called the Immigration and Nationality Act (INA) . The INA allows the United States to grant permission to settle in the country, and it determines whether a person is an alien, as well as the rights, duties, and obligations associated with being an alien in the United States.

The immigration experience is long and varied and has in many cases resulted in the development of multicultural societies; many modern states are characterized by a wide variety of cultures and ethnicities that have derived from previous periods of immigration. However, critics of the "melting pot" approach highlight the assimilation of diverse cultures and the repression of difference in the name of the state.