In graphical computing, a desktop environment (DE, sometimes desktop manager) offers a graphical user interface (GUI) to the computer. The name is derived from the desktop metaphor used by most of these interfaces, as opposed to the earlier, textual command line interfaces (CLI). A DE typically provides icons, windows, toolbars, folders, wallpapers, and abilities like drag and drop. As a whole, the particularities of design and function of a desktop environment endow it with a distinctive look and feel.

The desktop environments for the popular proprietary operating systems Microsoft Windows and Mac OS X are, in their intended use, relatively unalterable. This imposes a consistent user experience. However, there are alternative themes and third-party software that can completely change both the appearance of common interface elements (such as windows, buttons and icons) and the interface model itself. In Windows, this is accomplished by replacing the default Explorer shell.

Apple had the first desktop environment on a personal computer, featured on the lisa.

On systems running the X Window System (typically Unix-like systems), the desktop environment is much more flexible. In this context, a DE typically consists of a window manager (such as Metacity or KWin), a file manager (such as Konqueror or Nautilus), a set of themes, and programs and libraries for managing the desktop. All of these individual modules can be exchanged and individually configured to achieve a unique combination, but most desktop environments provide a default configuration that requires minimal user input.

Not all of the program code that is part of a DE has effects which are directly visible to the user. Some of it may be low-level code. KDE, for example, provides so-called KIOslaves which give the user access to a wide range of virtual devices. These I/O slaves are not available outside the KDE environment.