A justice ministry, ministry of justice, or department of justice, is a ministry or other government agency in charge of the administration of justice. The ministry or department is often headed by a minister of justice (minister for justice in a very few countries) or a secretary of justice. In some countries, the head of the department may be called the attorney general, for example in the United States. Monaco is an example of a country that does not have a ministry of justice, but rather a Directorate of Judicial Services (head: Secretary of Justice) that oversees the administration of justice. Vatican City, a country under the sovereignty of the Holy See, also does not possess a ministry of justice. Instead, the Governorate of Vatican City State (head: President of the Governorate of Vatican City State), the legislative body of the Vatican, includes a legal office.

Depending on the country, specific duties may relate to organizing the justice system, overseeing the public prosecutor and national investigative agencies (e.g. the American Federal Bureau of Investigation), and maintaining the legal system and public order. Some ministries have additional responsibilities in related policy areas such as overseeing elections, directing the police, law reform, and administration of the immigration and citizenship services. The duties of the ministry of justice may in some countries be split from separate responsibilities of an attorney general (often responsible for the justice system) and the interior minister (often responsible for public order). Sometimes the prison system is separated into another government department called Corrective Services.