A board of directors is a group of people who jointly supervise the activities of an organization, which can be either a for-profit business, nonprofit organization, or a government agency. Such a board's powers, duties, and responsibilities are determined by government regulations (including the jurisdiction's corporations law) and the organization's own constitution and bylaws. These authorities may specify the number of members of the board, how they are to be chosen, and how often they are to meet.

In an organization with voting members, the board is accountable to, and might be subordinate to, the organization's full membership, which usually vote for the members of the board. In a stock corporation, non-executive directors are voted for by the shareholders, with the board having ultimate responsibility for the management of the corporation. In nations with codetermination (such as Germany and Sweden), the workers of a corporation elect a set fraction of the board's directors. The board of directors appoints the chief executive officer of the corporation and sets out the overall strategic direction. In corporations with dispersed ownership, the identification and nomination of directors (that shareholders vote for or against) are often done by the board itself, leading to a high degree of self-perpetuation. In a non-stock corporation with no general voting membership, the board is the supreme governing body of the institution, and its members are sometimes chosen by the board itself.