Welland Canal (officially Welland Ship Canal), a waterway in Ontario, Canada. It allows ships to bypass Niagara Falls and is a major link in the Great Lakes-St. Lawrence Seaway system. The canal extends for 27 miles (43 km) from Port Weller on Lake Ontario to Port Colborne on Lake Erie.
Eight locks along the canal overcome the 320-foot (98-m) difference between the levels of Lakes Ontario and Erie. They vary in size but are at least 80 feet (24 m) wide and 859 feet (262 m) long, and can handle virtually all Great Lakes ships and most oceangoing vessels. Three of the locks are of twin construction, enabling ships moving in opposite directions to pass through at the same time. Canada's St. Lawrence Seaway Authority operates and maintains the locks.
The first Welland Canal, a shallow channel with wooden locks, was privately built during 1824–29. It was bought by the Canadian government in 1841, enlarged twice before 1913, and completely rebuilt by 1932. The canal was deepened as part of the St. Lawrence Seaway project, completed in 1959. Major improvements between 1967 and 1973 included the construction of a new, 8.3-mile (13.4-km) channel to replace a narrow, congested section of the waterway that curved through the city of Welland.