Independent agencies of the United States federal government are those agencies that exist outside of the federal executive departments (those headed by a Cabinet secretary) and the Executive Office of the President. In a more narrow sense, the term may also be used to describe agencies that, while constitutionally part of the executive branch, are independent of presidential control, usually because the president's power to dismiss the agency head or a member is limited.
Established through separate statutes passed by the Congress, each respective statutory grant of authority defines the goals the agency must work towards, as well as what substantive areas, if any, over which it may have the power of rulemaking. These agency rules (or regulations), when in force, have the power of federal law.
Independent agencies can be distinguished from the federal executive departments and other executive agencies by their structural and functional characteristics. Congress can also designate certain agencies explicitly as "independent" in the governing statute, but the functional differences have more legal significance.
While most executive agencies have a single director, administrator, or secretary appointed by the President of the United States, independent agencies (in the narrower sense of being outside presidential control) almost always have a commission, board, or similar collegial body consisting of five to seven members who share power over the agency. (This is why many independent agencies include the word "Commission" or "Board" in their name.) The president appoints the commissioners or board members, subject to Senate confirmation, but they often serve terms that are staggered and longer than a four-year presidential term, meaning that most presidents will not have the opportunity to appoint all the commissioners of a given independent agency. The president can normally designate which commissioner will serve as the chairperson. Normally there are statutory provisions limiting the president's authority to remove commissioners, typically for incapacity, neglect of duty, malfeasance, or other good cause. In addition, most independent agencies have a statutory requirement of bipartisan membership on the commission, so the president cannot simply fill vacancies with members of his own political party.