A ministry is a department of a government, led by a minister. Ministries are usually subordinate to the cabinet, and prime minister, president or chancellor. A government will usually have numerous ministries, each with a specialised field of service. National ministries vary greatly between countries, but some common ones include Ministry of Defence, Ministry of Foreign Affairs, Ministry of Finance, and Ministry of Health.

Some countries such as Sweden, Norway, Switzerland, the Philippines and the United States do not use the term "ministry" for their government departments, and instead simply call them departments. In Hong Kong the term "bureau" is used. Mexico calls ministries secretariats.

In Canada, some provincial-level government departments are called "ministries" (such as in Ontario and British Columbia) but most, along with their federal analogues, are termed "departments." Their heads are referred to as "ministers" in both levels of government, however. The specific tasks assigned to a minster is refered to as his "portfolio".