The Tees River is a major river in northeast England, flowing approximately 85 miles (137 kilometers) from its source in the Pennines to the North Sea. It passes through several towns, including Darlington and Stockton-on-Tees, and is known for its scenic landscapes and diverse wildlife. Historically, the Tees River played a significant role in the industrial development of the region, particularly during the 19th century. The river's estuary at Teesport is one of the busiest ports in the UK, facilitating trade and transportation. Today, the river is also popular for recreational activities like fishing and boating.