An office is a space where the employees of an organization perform administrative work in order to support and realize the various goals of the organization. The word "office" may also denote a position within an organization with specific duties attached to it (see officer, office-holder, official); the latter is an earlier usage, office as place originally referring to the location of one's duty. In the adjective form, the term "office" may refer to business-related tasks. In law, a company or organization has offices in any place where it has an official presence, even if that presence consists of a storage silo, for example, instead of a more traditional establishment with a desk and chair. An office is also an architectural and design phenomenon: including small offices, such as a bench in the corner of a small business or a room in someone's home (see small office/home office), entire floors of buildings, and massive buildings dedicated entirely to one company. In modern terms, an office is usually the location where white-collar workers carry out their functions.

Offices were, in classical antiquity, often part of a palace complex or a large temple. In theHigh Middle Ages (1000–1300), the medieval chancery, served as a sort of office, being the space where records and laws were stored and copied. With the growth of large, complex organizations in the 18th century, the first purpose-built office spaces were constructed. As the Industrial Revolution intensified in the 18th and 19th centuries, the industries of banking, rail, insurance, retail, petroleum, and telegraphy grew dramatically, requiring many clerks, and as a result, more office space was assigned to house their activities. The time-and-motion study, pioneered in manufacturing by F. W. Taylor (1856-1915) led to the "Modern Efficiency Desk" of 1915 with a flat top and drawers below, designed to allow managers an easy view of the workers. By the middle of the 20th century, it became apparent that an efficient office required discretion in the control of privacy, and gradually the cubicle system evolved.

The main purpose of an office building is to provide a working environment for primarily administrative and managerial workers. Work spaces within offices are typically used for conventional office activities such as reading, writing, and computer work. Workers usually occupy set areas within the office building and usually are provided with desks, PCs, and other equipment they may need within their areas. The interior of the office may or may not have internal walls, barriers, or cubicles separating individual workers from one another. In addition to individual workspaces, many offices contain meeting rooms, lounges, and spaces for support activities, such as photocopying and filing. Some offices also have a kitchen area where workers can make their lunches. There are many different ways of arranging the space in an office based on function, managerial styles, and the culture of specific companies. While offices can be built in almost any location and almost any building, some modern requirements for offices make this more difficult, such as requirements for light, networking, and security.