The Leeds Northern Railway (LNR), originally the Leeds and Thirsk Railway, was an English railway company that built and opened a line from Leeds to Stockton via Harrogate and Thirsk. In 1845 the Leeds and Thirsk Railway received permission for a line from Leeds to Thirsk, part of which opened in 1848, but problems building the Bramhope Tunnel delayed trains operating into Leeds until 1849.
The Leeds and Thirsk Railway Company changed its name to the Leeds Northern Railway on 3 July 1851 before its line to Stockton opened. The company formed an alliance with the West Hartlepool Harbour & Railway and was involved in a price war with the York, Newcastle & Berwick Railway (YN&BR). A merger of the YN&BR with the LNR and the York & North Midland Railway was accepted by LNR shareholders, and by royal assent on 31 July 1854 the three companies merged to become the North Eastern Railway.
Today, sections of the former Leeds Northern Railway line form the Harrogate Line between Leeds and Harrogate, and the Northallerton to Stockton Line.