A board of directors is a body of elected or appointed members who jointly oversee the activities of a company or organization. The body sometimes has a different name, such as board of trustees, board of governors, board of managers, or executive board. It is often simply referred to as "the board."

A board's activities are determined by the powers, duties, and responsibilities delegated to it or conferred on it by an authority outside itself. These matters are typically detailed in the organization's bylaws. The bylaws commonly also specify the number of members of the board, how they are to be chosen, and when they are to meet.

In an organization with voting members, e.g., a professional society, the board acts on behalf of, and is subordinate to, the organization's full assembly, which usually chooses the members of the board. In a stock corporation, the board is elected by the stockholders and is the highest authority in the management of the corporation. In a nonstock corporation with no general voting membership, e.g., a university, the board is the supreme governing body of the institution.

Typical duties of boards of directors include

• governing the organization by establishing broad policies and objectives;
• selecting, appointing, supporting and reviewing the performance of the chief executive;
• ensuring the availability of adequate financial resources;
• approving annual budgets;
• accounting to the stakeholders for the organization's performance.

The legal responsibilities of boards and board members vary with the nature of the organization, and with the jurisdiction within which it operates. For public corporations, these responsibilities are typically much more rigorous and complex than for those of other types.

Typically the board chooses one of its members to be the chair or chairperson of the board of directors, traditionally also called chairman or chairwoman.

Corporations

Theoretically, the control of a company is divided between two bodies: the board of directors, and the shareholders in general meeting. In practice, the amount of power exercised by the board varies with the type of company. In small private companies, the directors and the shareholders will normally be the same people, and thus there is no real division of power. In large public companies, the board tends to exercise more of a supervisory role, and individual responsibility and management tends to be delegated downward to individual professional executive directors (such as a finance director or a marketing director) who deal with particular areas of the company's affairs.

Another feature of boards of directors in large public companies is that the board tends to have more de facto power. Between the practice of institutional shareholders (such as pension funds and banks) granting proxies to the board to vote their shares at general meetings and the large numbers of shareholders involved, the board can comprise a voting bloc that is difficult to overcome. However, there have been moves recently to try to increase shareholder activism amongst both institutional investors and individuals with small shareholdings. A board-only organization is one whose board is self-appointed, rather than being accountable to a base of members through elections; or in which the powers of the membership are extremely limited.