Kingston (Ontario), city, seat of Frontenac County in southeastern Ontario, Canada. It is on Lake Ontario at the mouth of the St. Lawrence River and at the southern terminus of the Rideau Canal. It is a shipping, manufacturing, and educational center. The city grew as a manufacturer of fabricated metal, diesel equipment, synthetic fibers, electronic products, ceramics, and processed food. Economic activities associated with tourism, healthcare, and information services grew in importance at the end of the 20th century and beginning of the new millennium.

Several educational institutions are in Kingston, including Queen’s University at Kingston, the affiliated Queen's Theological College, and the Royal Military College of Canada. It is also home to Bellevue House National Historic Site, which is the former home of Sir John A. Macdonald, the first prime minister of Canada, and Fort Henry, which was built during the War of 1812 and now houses a museum. Additional attractions include the MacLachlan Woodworking Museum; the Marine Museum of the Great Lakes; cruises of the Thousand Islands; the Agnes Etherington Art Centre; and the International Ice Hockey Federation Museum.

Established in 1673 as a French trading post, the community developed around Fort Frontenac until the British captured the fort in 1758. The land was then ceded to the British. In 1783 and 1784 the site was resettled by United Empire Loyalists, who named it King’s Town after George III of England. From 1841 to 1844 Kingston served as the capital of the United Province of Canada. It incorporated as a city in 1846. As commercial activities declined toward the end of the 19th century, institutional employers such as the university, penitentiaries, hospitals, and the military became more important to the city's economy. Their importance continued through the 20th century. In 1998 the city of Kingston reincorporated when it amalgamated with Kingston and Pittsburgh townships.

Kingston covers a land area of 29.6 sq km (11.4 sq mi). Population 107,840 (1991); 114,195 (2001).