The Nexen Building is a high rise office building in downtown Calgary, Alberta, Canada. It is a 37-storey skyscraper, with a height of 152 m (499 ft). The commissioner and main tenant of the building is the Canadian energy company Nexen. It was designed by CPV Group Architects and Engineers Ltd and built by CANA Construction Company Limited. The late modernist building was completed in 1982. The Nexen Building (formerly the Nova Corporation headquarters building) employs a composite stub-girder steel frame floor system, originally developed in part by Joseph Colaco.