An office building (also called an "office block") is an enclosed structure in which some type of office forms a primary usage. Office buildings house workplaces where non-manual activity takes place mainly at desks, at tables, and in meeting rooms.

Tenants in an office building can be any commercial lessees or owner-tenants, institutions (like universities, hospitals, and non-profits), governments and their various branches, and any other such organizations.

For the most part, space in an office building is not designed for customer interactions or services, although many of them house retail space, especially on the ground floor. Service areas like bank branches are not normally considered office buildings unless a large part of their space is devoted to "behind-the-scenes" administrative functions.