John Ewart (January 31, 1788 – September 18, 1856) was a Canadianarchitect and businessman.
He was born in TranentScotland in 1788. After completing his apprenticeship in building, he moved to London around 1811. In 1816, he emigrated to New York City and moved to York (Toronto) in Upper Canada a few years later. He built a hospital and then the town's first Roman Catholic church, St. Paul's. In 1818, he built the parliament building for Upper Canada at York. In 1824, he designed the courthouse and jail for the Home District and, in 1827–31, the two-story castellated-style courthouse for the London District, Ontario. He was one of the overseers for the construction of the new parliament building after the original building burned in 1824. In 1829, he prepared the design for the original Osgoode Hall; some remodelling and additions occurred later. He continued to operate a building yard and was a director on the boards of several institutions in the city after 1830, although he had retired as an architect.