The US$500 million (£281 million) project for EnCana Corporation, the country's largest natural-gas producer, will become the first major commercial scheme east of Centre Street in downtown Calgary.
It is understood that the building will be the tallest to be built in Canada for nearly two decades and will have a 'strong impact on the urban context'.
Describing his appointment, Norman Foster said: 'We are thrilled to have this opportunity to meet EnCana's business objectives with the design of a new office complex - to capture the collective consciousness of Calgary and to articulate the philosophy of an ambitious and progressive tenant.
'We hope to set a bold precedent for the high-quality, environmentally sustainable development of the downtown area while responding to the civic values of the city.'
Construction is due to start on site in 2007 and the building is scheduled to open its doors in 2010.