St. Catharines is the most populous city in Canada's Niagara Region, the eighth largest urban area in the province of Ontario. As of 2021, St. Catharines has an area of 96.20 square kilometres (37.14 sq mi) and 136,803 residents. It lies in Southern Ontario, 51 kilometres (32 mi) south of Toronto across Lake Ontario, and is 19 kilometres (12 mi) inland from the international boundary with the United States along the Niagara River. It is the northern entrance of the Welland Canal. St. Catharines carries the official nickname "The Garden City" due to its 1,000 acres (4 km) of parks, gardens, and trails.
St. Catharines is between the Greater Toronto and Hamilton Area (GTHA) and the Canada–U.S. border at Fort Erie. Manufacturing was the city's dominant industry, as noted by the heraldic motto, "Industry and Liberality". General Motors of Canada, Ltd., the Canadian subsidiary of General Motors, was the city's largest employer, a distinction now held by the District School Board of Niagara. THK Rhythm Automotive, formerly TRW, operates a plant in the city, although in recent years, employment there has shifted from heavy industry and manufacturing to services.