Workbench is the desktop environment and graphical file manager of AmigaOS developed by Commodore International for their Amiga line of computers. Workbench provides the user with a graphical interface to work with file systems and launch applications. It uses a workbench metaphor (in place of the more common desktop metaphor) for representing file system organisation.

"Workbench" was also the name originally given to the entire Amiga operating system up until version 3.1. From release 3.5 the operating system was renamed "AmigaOS" and subsequently "Workbench" refers to the graphical front end only.

The Amiga Workbench uses the metaphor of a workbench (i.e. a workbench for manual labor), rather than the now-standard desktop metaphor, for representing file system organization. The desktop itself is called Workbench and uses the following representations: drawers (instead of folders) for directories, tools for executable programs, projects for data files, and a trash can as a folder intended to contain deleted files. These representations may be considered somewhat unusual by a modern user, but at the time there were no commonly accepted metaphors and Commodore chose to use different idioms from their competitors (Apple had already pursued legal action to prevent other software companies from offering graphical user interfaces similar to its own). Workbench is a spatial file manager in the sense that it uses a spatial metaphor to represent files and folders as if they are real physical objects. Under this concept, each drawer (folder) opens in its own window, rather than within a single browser under the now more common navigational concept.

Workbench utilizes the Amiga's native windowing system called Intuition to provide the graphical user interface. Intuition manages the rendering of screens, windows, and gadgets (graphical elements, equivalent to widgets). Later versions of AmigaOS enhanced the interface with more complex object-oriented widget systems, such as gadtools.library and BOOPSI (AmigaOS 2.0 and later) and ReAction (AmigaOS 3.5 and later). Intuition also handles user input events, such as, input from the keyboard and mouse. Workbench requires a two button mouse, where right click operates pull-down menus and left click is used for all other purposes.

The underlying AmigaOS allows the Workbench to launch multiple applications that can execute concurrently. This is achieved through Exec, the Amiga's multi-tasking kernel, which handles memory management, message passing, and task scheduling. Applications launched from Workbench could report their success back to Workbench, but this was not a requirement and few actually did. Workbench itself has always been a disk-based component, though much of the underlying functionality is stored in the Amiga's Kickstart firmware, usually stored in ROM. As a consequence, it is necessary to boot from a system disk to launch Workbench. This setup streamlines the process of launching games (which typically do not require Workbench) and ensures that memory is not used unnecessarily by the OS in memory-limited systems. Workbench was shipped with all Amiga models from Commodore. Workbench was provided either on floppy disk or later (as part of AmigaOS) on CD-ROM. Initially, Workbench was designed to be launched and operate from floppy disk (or other removable media). Later versions could be installed on hard disk, for which an installer was developed for use with AmigaOS 2.0 and later. AmigaOS (including Workbench) often came pre-installed on systems shipped with hard disks.

Up until and including release 3.1 of the Amiga's operating system, Commodore itself used the specific term Workbench to refer to the entire Amiga operating system of itself – Distinctively, AmigaDOS was more referred to specifically in connexion with the Amiga's Command-line interface CLI, called Shell. As a consequence Workbench was commonly used to refer to both, the operating system and the file manager component. For end users, Workbench was often synonymous with the Amiga's OS.

Notably from the first versions of 3rd-party releases from licensed contractors like version 3.5 onwards, the OS was successively called "AmigaOS" and pre-3.5 versions may also retroactively referred to as "AmigaOS" (rather than Workbench). Subsequently, "Workbench" refers to the native graphical file manager only, in contrast to the Amiga's ROM-located parts of the OS in its "Kickstart".

From its inception, Workbench offered a highly customizable interface. The user could change the aspect of program icons replacing it with newer ones with different color combinations. Users could also take a "snapshot" of icons and windows so the icons will remain on the desktop at coordinates chosen by user and windows will open at the desired size.