Oswego is a city in and the county seat of Oswego County, New York, United States. The population was 16,921 at the 2020 census. Oswego is situated at the mouth of the Oswego River on the southeastern shore of Lake Ontario in Upstate New York, about 40 miles (64 km) northwest of Syracuse and 74 miles (119 km) east-northeast of Rochester by road. The city promotes itself as "The Port City of Central New York".