Nexen Building, Calgary, Office skyscraper in Downtown, Calgary, Canada.

The Nexen Building is a 37-story office tower that reaches 152 meters high in downtown Calgary. Its facade features stainless steel and curtain wall construction at 801 Seventh Avenue Southwest.

The building was constructed in 1982 and initially served as headquarters for NOVA Corporation. After 2000, its purpose and occupancy changed multiple times over the following decades.

The tower sits diagonally on its lot rather than aligned to the downtown street grid, so its faces meet Seventh Avenue at an angle. The original tenant was NOVA Corporation, and the building carried the Nexen name from 2000 until the company moved out in 2019. In 2025 the University of Calgary's School of Architecture, Planning and Landscape took a lease on the Annex and nine floors.

The tower occupies a full block at 801 Seventh Avenue S.W., between the downtown grid streets, so its diagonal footprint is easiest to read from the corner sidewalks at Seventh Avenue and the cross streets. The building was vacant from 2019 to 2025, and the University of Calgary's School of Architecture, Planning and Landscape began leasing the Annex and nine floors in 2025, so interior access is tied to the university rather than to public visiting.

The floor system, a composite stub-girder steel frame, was developed in part by engineer Joseph Colaco. It lets the tower carry open office floors without interior support columns, a structural choice tied to the building's 1982 completion.