The Spinnaker Tower is a 170m (558 ft) high tower situated in Portsmouth, United Kingdom. The tower is the centrepiece of the redevelopment of Portsmouth Harbour, which was supported by a large National Lottery grant. The tower, designed by Local Firm HGP Architects and the engineering consultants Scott Wilson, celebrates Portsmouth's maritime tradition, a theme central to the design. After several years of delays and a massive budget overspend, it was officially opened on 18 October 2005, and is expected to draw many new tourists to the area.

The tower, at a height of 170 metres (558 feet) above Ordnance Datum, is two and a half times the height of Nelson's Column, making it the tallest accessible structure in the United Kingdom outside of London. The tower is visible from miles around Portsmouth, changing the horizon across the south coast.

The tower represents sails billowing in the wind, a design accomplished using two large, white, sweeping steel arcs, which give the tower its distinctive spinnaker sail design. At the top is a triple observation deck, providing a 320 degree view of the city of Portsmouth, the Langstone and Portsmouth harbours, and a viewing distance of 37 kilometres (23 miles). The glass floor is the largest in Europe.

This design was chosen from a selection of concept designs through a vote offered to Portsmouth residents.

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