An observation tower is a tower used to view events from a long distance and to create a full 360 degree range of vision to conduct long distance observations. Observation towers are usually at least 20 metres (66 ft) tall and are made from stone, iron, and wood. Many modern towers are also used as TV towers, restaurants, or churches. The towers first appeared in the ancient world, as long ago as the Babylonian Empire.

Observation towers that are used as guard posts or observation posts over an extended period to overlook an area are commonly called watchtowers instead.

Similar instances of observation towers are recognised as crow's nests, observatories, viewing platforms, etc.

Observation towers are an easily visible sight on the countryside, as they must rise over trees and other obstacles to ensure clear vision. Older control rooms have often been likened to medieval chambers. The heavy use of stone, iron, and wood in their construction helps to create this illusion. Modern towers frequently have observation decks or terraces with restaurants or on the roof of mountain stations of an aerial ropeway. Frequently observation towers are used also as location of radio services within the UHF/VHF range (FM sound broadcasting, TV, public rural broadcasting service, and portable radio service). In some cases this usage of the tower is at least as important as its use as an observation tower. Such towers are usually called TV towers or telecommunication towers. Many towers are also equipped with a tower restaurant and allow visitors access via elevators. Also common is the usage of water towers as observation towers. As in the case of TV towers the visitor will usually reach the observation deck by elevator, which is usually at a lower height above ground The typical height of the observation deck of water towers is 20 metres up to 50 metres, while the typical height of the platform of TV towers is from 80 metres up to 200 metres. Finally, some church towers may have observation decks, albeit often without an elevator. Many other buildings may have towers which allow for observation.

In particular prior to World War I rambler associations, and some municipalities, built observation towers on numerous summits. Usually these towers were built of stone, however sometimes wood or iron was also used. At nearly all these towers access to the observation deck, usually at a height of between 5 and 40 metres, is only possible by way of stairs. Most of these towers are used only for tourism, however some of these towers might also be used, at times of high forest fire risk, as fire observation posts or in times of war as military observation posts with anti-aircraft positions placed beside it. Further uses were not intended at most of these buildings, although some of these towers today now carry antennas for police/fire engine radios, portable radio or low power FM- and TV-transmitters. Older observation towers frequently have a flag pole at its top.

Some of these towers are permanently accessible, either free or with the payment of an admission fee. Others are accessible only at certain times, in most cases only with the payment of an admission fee. At these towers the platform is usually open, with some having a restaurant in the basement. There are also towers with a much more extensive use; for example, the observation tower on Rossberg mountains in Reutlingen contains a hotel within its structure.

Although most of these towers were initially built before World War I, such structures are still being built, in particular as attractions at horticultural shows. Modern observation towers are in most cases no longer built of brick, but concrete, steel and wood are used as the preferred building materials.

Permanent observation towers are also sometimes found in amusement parks, however in parks where each attraction is not separately paid for, panorama rides are preferred.^{[citation needed]}