List of tallest buildings in Ontario

This list of tallest buildings in Ontario ranks skyscrapers and high rise buildings in the province of Ontario by height. Buildings in nine cities are included in this list; Hamilton, Kitchener, London, Markham, Mississauga, Niagara Falls, Ottawa, Toronto, and Windsor, each having buildings taller than 100 metres.

The tallest building in the province of Ontario is First Canadian Place 298 metres (978 feet). Completed in 1976, it is also the tallest building in Canada and the 68th tallest building in the world. At the time of its completion, it was the tallest building in the world outside of Chicago and New York City.

Due to height restrictions, tall skyscrapers are restricted in many parts of Ottawa, including the downtown core. Initially the height restrictions were put in place as to prevent any building from exceeding the height of the Peace Tower of Parliament Hill. The tallest building in that city now rises to 143 m.

In recent years, a development boom has caused many cities, that historically haven’t had tall buildings or dense urban cores, to densify and construct taller buildings like Kitchener, Windsor, Markham, etc.

Buildings over 100 meters
This list ranks buildings in Ontario that stand between least 100 m (328 ft) tall, based on CTBUH height measurement standards. This includes spires and architectural details but does not include antenna masts. An equal sign (=) following a rank indicates the same height between two or more buildings. Freestanding observation and/or telecommunication towers, while not habitable buildings, are included for comparison purposes; however, they are not ranked. One such tower is the CN Tower.

By city

 * List of tallest buildings in Hamilton, Ontario
 * List of tallest buildings in London, Ontario
 * List of tallest buildings in Ottawa–Gatineau
 * List of tallest buildings in Mississauga
 * List of tallest buildings in Niagara Falls, Ontario
 * List of tallest buildings in Greater Sudbury
 * List of tallest buildings in Toronto
 * List of tallest buildings in the Waterloo Regional Municipality
 * List of tallest buildings in Windsor, Ontario