The Tees Valley Line is a rail route, in Northern England, following part of the original Stockton and Darlington Railway route of 1825. The line covers a distance of 38 miles (61 km), and connects Bishop Auckland to Saltburn via Darlington, Middlesbrough and 14 other stations in the Teesdale.

The Stockton and Darlington Railway (S&DR) was a railway company that operated in north-east England from 1825 to 1863. The world's first public railway to use steam locomotives, its first line connected collieries near Shildon with Darlington and Stockton in County Durham, and was officially opened on 27 September 1825. The movement of coal to ships rapidly became a lucrative business, and the line was soon extended to a new port at Middlesbrough. While coal waggons were hauled by steam locomotives from the start, passengers were carried in coaches drawn by horses until carriages hauled by steam locomotives were introduced in 1833.