The United States Immigration and Naturalization Service (INS) was a part of the United States Department of Justice and handled legal and illegal immigration and naturalization. It ceased to exist on March 1, 2003.

Most of its functions were transferred to three new agencies within the newly created Department of Homeland Security in March 2003. The administration of immigration services, including permanent residence, naturalization, asylum, and other functions became the responsibility of the Bureau of Citizenship and Immigration Services (BCIS), which existed only for a short time before changing to its current name, U.S. Citizenship and Immigration Services (USCIS). The investigative and enforcement functions (including investigations, deportation, and intelligence) were combined with U.S. Customs investigators, the Federal Protective Service, and the Federal Air Marshal Service, to create U.S. Immigration and Customs Enforcement (ICE). The border functions of the INS, which included the Border Patrol along with INS Inspectors, were combined with U.S. Customs Inspectors into the newly created U.S. Customs and Border Protection (CBP).