Immigration law refers to national government policies which control the phenomenon of immigration to their country.

Immigraton law, regarding foreign citizens, is related to nationality law, which governs the legal status of people, in matters such as citizenship. Immigration laws vary from country to country, as well as according to the political climate of the times, as sentiments may sway from the widely inclusive to the deeply exclusive of new immigrants.

Immigration law regarding the citizens of a country is regulated by international law. The United Nations International Covenant on Civil and Political Rights mandates that all countries allow entry to its own citizens.

Certain countries may maintain rather strict laws which regulate both the right of entry and internal rights, such as the duration of stay and the right to participate in government. Most countries have laws which designate a process for naturalization, by which immigrants may become citizens.

The immigration laws in the United States have experienced uneven progress. During colonial times independent colonies created their immigration laws. The first attempt to naturalize foreigners was through the Naturalization Act of 1790. However many years later the Chinese Exclusion Act was passed to stop the immigration of Chinese people. The Immigration Act of 1924 put a quota on how many immigrants are permitted, based on nationality. The Immigration and Nationality Act of 1952 led to the creation of the Immigration and Naturalization Service.