The Prime Tower, also named "Maag-Tower" in an earlier stage of planning, is an skyscraper in Zürich, Switzerland, used mainly as office space. At a height of 126 metres (413 ft), it was the tallest building in Switzerland from 2011 until 2015, when the Roche Tower in Basel (standing at 178 m (584 ft)) was completed.

The building is located near the Hardbrücke railway station in Zürich West of the Industriequartier. The tower replaced an industrial facility.

According to its developers, the tower's construction, which took 15 years to plan and execute, was a financial success, with its valuation based on lease rates exceeding the construction cost by CHF 110 million.

A webcam on top of the building offers a 360° view of Zürich.

The tower and its two companion buildings, Cubus and Diagonal, are used primarily as office buildings. As of its opening in December 2011, the tower hosts the "Clouds" bar and restaurant on its top floor, a conference center, the Hotel Rivington & Sons on the ground floor, as well as the offices of Deutsche Bank Schweiz, Homburger AG, Transammonia, Korn/Ferry International, Citibank Switzerland, Infosys, Repower AG, Ernst & Young, Zürcher Kantonalbank, Nexxiot AG and consulting companies.

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  Prime Tower at night.
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  Prime Tower from the ground at night.
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  Main entrance of the Prime Tower at night.
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  Prime Tower in daylight.
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  View from Clouds restaurant at the top of Prime Tower.
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  Prime Tower construction site at night, showing Marti's wind barrier system.

• Media related to Prime Tower (Zürich) at Wikimedia Commons
• Prime Tower website
• Webcam summary from April 2008 to October 2011
• Time-lapse movie of the tower's construction on YouTube