Sudbury (Ontario), city in southeastern Ontario, Canada, on Ramsey Lake. It is the judicial seat for Sudbury District. Sudbury is a commercial, manufacturing, educational, and transportation center situated in a major nickel- and copper-mining area. Products include processed ore, chemicals, construction materials, foodstuffs, beverages, fabricated metal, machinery, and printed materials. The city is served by Sudbury Airport.

Laurentian University (bilingual, French/English), two junior colleges (one French, one English), and several research institutes for mining are located in the city. Points of interest include Science North, a hands-on science center where visitors can learn about the Sudbury Neutrino Observatory (located west of the city). Sudbury is also home to the Flour Mill Heritage Museum; the Copper Cliff Museum; the Art Gallery of Sudbury; the Northern Ontario Railroad Museum and Heritage Centre; and the Lake Laurentian Conservation Area. The Sudbury Wolves hockey team plays at the Sudbury Arena. Annual events include the Canadian Garlic Festival and the Northern Lights Festival Boreal, both in summer, and the Cinéfest international film festival in autumn.

Settlement of the community began in 1883, when the railroad was built and great mineral deposits were discovered in the area. It is named for Sudbury, England. Incorporated as a town in 1893 and as a city in 1930, Sudbury grew gradually until after World War II (1939-1945), when it began to expand rapidly. In the early 1980s Sudbury undertook one of the world's largest urban land-reclamation projects, for which it received numerous environmental awards. It actively diversified its economy in the 1980s and experienced growth in the health, financial, education, and tourism sectors.

Sudbury covers a land area of 262.7 sq km (101.4 sq mi). Population 92,884 (1991); 155,219 (2001).