A hierarchical organization or hierarchical organisation (see spelling differences) is an organizational structure where every entity in the organization, except one, is subordinate to a single other entity. This arrangement is a form of hierarchy. In an organization, this hierarchy usually consists of a singular/group of power at the top with subsequent levels of power beneath them. This is the dominant mode of organization among large organizations; most corporations, governments, criminal enterprises, and organized religions are hierarchical organizations with different levels of management power or authority. For example, the broad, top-level overview of the hierarchy of the Catholic Church consists of the Pope, then the Cardinals, then the Archbishops, and so on. Another example is the hierarchy between the four castes in the Hindu caste system, which arises from the religious belief "that each is derived from a different part of the creator God’s (Brahma) body, descending from the head downwards."

Members of hierarchical organizational structures mainly communicate with their immediate superior and their immediate subordinates. Structuring organizations in this way is useful, partly because it reduces the communication overhead costs by limiting information flows.

A hierarchy is typically visualized as a pyramid, where the height of the ranking or person depicts their power status and the width of that level represents how many people or business divisions are at that level relative to the whole—the highest-ranking people are at the apex, and there are very few of them, and in many cases only one; the base may include thousands of people who have no subordinates. These hierarchies are typically depicted with a tree or triangle diagram, creating an organizational chart or organogram. Those nearest the top have more power than those nearest the bottom, and there being fewer people at the top than at the bottom. As a result, superiors in a hierarchy generally have higher status and obtain higher salaries and other rewards than their subordinates.

Although the image of organizational hierarchy as a pyramid is widely used, strictly speaking such a pyramid (or organizational chart as its representation) draws on two mechanisms: hierarchy and division of labour. As such, a hierarchy can, for example, also entail a boss with a single employee. When such a simple hierarchy grows by subordinates specialising (e.g. in production, sales, and accounting) and subsequently also establishing and supervising their own (e.g. production, sales, accounting) departments, the typical pyramid arises. This specialisation process is called division of labour.

Governmental organizations and most companies feature similar hierarchical structures. Traditionally, the monarch stood at the pinnacle of the state. In many countries, feudalism and manorialism provided a formal social structure that established hierarchical links pervading every level of society, with the monarch at the top.

In modern post-feudal states the nominal top of the hierarchy still remains a head of state – sometimes a president or a constitutional monarch, although in many modern states the powers of the head of state are delegated among different bodies. Below or alongside this head there is commonly a senate, parliament or congress; such bodies in turn often delegate the day-to-day running of the country to a prime minister, who may head a cabinet. In many democracies, constitutions theoretically regard "the people" as the notional top of the hierarchy, above the head of state; in reality, the people's influence is often restricted to voting in elections or referendums.

In business, the business owner traditionally occupies the pinnacle of the organization. Most modern large companies lack a single dominant shareholder and for most purposes delegate the collective power of the business owners to a board of directors, which in turn delegates the day-to-day running of the company to a managing director or CEO. Again, although the shareholders of the company nominally rank at the top of the hierarchy, in reality many companies are run at least in part as personal fiefdoms by their management. Corporate governance rules attempt to mitigate this tendency.

Smaller and more informal social units – families, bands, tribes, special interest groups – which may form spontaneously, have little need for complex hierarchies – or indeed for any hierarchies. They may rely on self-organizing tendencies. A conventional view ascribes the growth of hierarchical social habits and structures to increased complexity; the religious syncretism and issues of tax-gathering in expanding empires played a role here.