A government agency is a department of a local or national government responsible for the oversight and administration of a specific function, such as a customs agency or a space agency.

Examples include Environment Agency of England and Wales and the Environmental Protection Agency in the United States.

Government agencies of the United Kingdom

Agencies in the United Kingdom are either Executive Agencies answerable to government ministers or non-ministerial government departments answerable directly to one of the parliaments or devolved assemblies of the United Kingdom.

Agencies can be created by enabling legislation by the Parliament of the United Kingdom, Scottish Parliament or the National Assembly for Wales.

Agencies in England usually answer to Westminster or the British Government. In Scotland they usually answer to the Scottish Executive or the Scottish Parliament and in Wales to the National Assembly for Wales.

Some have remits that cover the entire UK and these organisations are funded by and answer to the British Government.

Government agencies in the United States

The Congress and President of the United States delegate specific authority to government agencies to regulate the complex facets of the modern American federal state. Also, most of the 50 U.S. states have created similar government agencies, but with limited, state-level regulatory power. The agencies of the federal government are often divided into two categories:

• United States Federal Executive Departments - that include the President's cabinet-level departments, and their sub-units, and
• Independent agencies of the United States government - that exercise some degree of independence from the President's control. Although the heads of Independent Agencies are often appointed by the President, they usually can only be removed for cause. The heads of Independent Agencies work together in groups, such as a commission, board or council. Independent Agencies often function as miniature versions of the tripartite federal government with the authority to legislate (through the issuing, or "promulgation" of regulations), to adjudicate disputes, and to enforce agency regulations (through enforcement personnel). Examples of independent agencies include the U.S. Securities and Exchange Commission (SEC), the National Labor Relations Board (NLRB) and the Federal Trade Commission (FTC).

Most federal agencies are created by Congress through statutes called "enabling statutes," that define the scope of an agency's authority. Because the Constitution does not expressly mention federal agencies (as it does the three branches), some commentators have called agencies the "headless fourth branch" of the federal government. However, most independent agencies are technically part of the executive branch, with a few located in the legislative branch of government. By enacting the Administrative Procedure Act (APA) in 1946, Congress established some means to oversee government agency action. The APA established uniform administrative law procedures for a federal agency's promulgation of rules, and adjudication of claims. The APA also sets forth the process for judicial review of agency action.