A board of directors is a body of elected or appointed members who jointly oversee the activities of a company or organization. Other names include board of governors, board of managers, board of regents, board of trustees, and board of visitors. 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 non-stock corporation with no general voting membership, e.g., a university, the board is the supreme governing body of the institution; its members are sometimes chosen by the board itself.