Ridley College is a private boarding and day university-preparatory school located in St. Catharines, Ontario, Canada, 20 miles (32 km) from Niagara Falls. The school confers the Ontario Secondary School Diploma and the International Baccalaureate diploma programme. Ridley is one of the oldest private schools in Canada, and has the largest boarding program in Ontario, with students representing over 55 countries.

St. Catharines is the most populous city in Canada's Niagara Region, the eighth largest urban area in the province of Ontario. As of 2017, St. Catharines has an area of 96.13 square kilometres (37.12 sq mi) and 140,370 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. Residents of St. Catharines are known as St. Catharinites. St. Catharines carries the official nickname "The Garden City" due to its 1,000 acres (4 km2) of parks, gardens, and trails.