Saint Thomas Tower, also known as Fort Saint Thomas, is a large bastioned watchtower in Marsaskala, Malta. It was built in 1614, the third of six Wignacourt towers. An artillery battery was added to the tower in the early 18th century. Saint Thomas Tower is the largest watchtower in Malta.

A watchtower or watch tower is a type of fortification used in many parts of the world. It differs from a regular tower in that its primary use is military and from a turret in that it is usually a freestanding structure. Its main purpose is to provide a high, safe place from which a sentinel or guard may observe the surrounding area. In some cases, non-military towers, such as religious towers, may also be used as watchtowers.