A clock tower is a tower specifically built with one or more (often four) clock faces. Clock towers can be either freestanding or part of a church or municipal building such as a town hall.

The mechanism inside the tower is known as a turret clock. It often marks the hour (and sometimes segments of an hour) by sounding large bells or chimes, sometimes playing simple musical phrases or tunes.

Some clocks towers are famously known landmarks. Five of the best-known are the Clock Tower, Palace of Westminster, which houses the Great Bell (generally known as Big Ben) in London, the Rajabai Tower in Mumbai, the Spasskaya Tower of the Moscow Kremlin, the Torre dell'Orologio in the Piazza San Marco in Venice, Italy, and Zytglogge clock tower in the Old city of Bern, Switzerland. The Royal Mecca Clock Tower in Saudi Arabia is the largest clock tower in the world.

On New Year's Eve 2004 four 6.3-meter clock faces were added to the top of the Warsaw Palace of Culture and Science building in Warsaw, Poland. This building is 231 m (757 ft) tall and is the second tallest clock tower in the world . The NTT DoCoMo Yoyogi Building is 240 meters (787 feet) high and is the tallest clock tower in the world. The Allen-Bradley Clock Tower is the tallest non-chiming four faced clock tower in the world.