An interior ministry is a government ministry typically responsible for policing

Police

The police is a personification of the state designated to put in practice the enforced law, protect property and reduce civil disorder in civilian matters. Their powers include the legitimized use of force...

, national security

National security

National security is the requirement to maintain the survival of the state through the use of economic, diplomacy, power projection and political power. The concept developed mostly in the United States of America after World War II...

, and immigration

Immigration

Immigration is the act of foreigners passing or coming into a country for the purpose of permanent residence...

 matters. The ministry is often headed by a minister of the interior or minister of home affairs. In some countries, matters relating to the maintenance of law and order and the administration of justice are the responsibility of a separate justice ministry.

In countries with a federal

Federation

A federation , also known as a federal state, is a type of sovereign state characterized by a union of partially self-governing states or regions united by a central government...

 constitution, an interior minister will often be found at both the federal and state levels.