According to the fourteenth amendment of the Constitution of the United States, all persons born or naturalized in the United States are citizens of the United States.

Most people become citizens of the United States for one of these ways:

-On-birth in the territory of the United States or U.S. citizen parents, or

Naturalization is the process by which the United States citizenship is granted to a foreign citizen or national after the person meets the requirements set by Congress in the Immigration and Nationality Act (INA). The general requirements for naturalization include:

- A period of residence and physical presence in the United States;
- Ability to read, write and speak English;
- Knowledge and understanding of U.S. history and government;
- Good moral character; and
- Compliance with the principles of the Constitution of the United States.

All applicants for naturalization must demonstrate good moral character, among other requirements. Some of the requirements for naturalization may be amended or are exempt, such as for spouses of American Citizens.