A viewscreen (or main viewer) was an audio/visual device used aboard starships, space stations, and at planetary facilities by space-faring organizations. These devices were used to display various types of images from sensor data and communications signals.

Generally consisting of a large screen or window located on the bridge of a starship (or operations center of a space station or starbase), the viewscreen was an almost universal facet of space exploration and colonization dating as far back as the 22nd century, surviving well into the 23rd, 24th and 25th centuries.

Typically used to display images of the area immediately around or in front of a starship, the viewscreen could provide views from all directions, as well as call up data from the library computer. It was also essential in ship-to-ship communication, allowing face-to-face conference if so desired, utilizing subspace and other communications systems.

Visual contact, however, could only be achieved when in visual range. When necessary, the image on the viewscreen could be magnified.