The Sheffield, Ashton-under-Lyne and Manchester Railway was an early British railway company which opened in stages between 1841 and 1845 between Sheffield and Manchester via Ashton-under-Lyne. The Peak District formed a formidable barrier, and the line's engineer constructed Woodhead Tunnel, over three miles (4.8 km) long. The company amalgamated with the Sheffield and Lincolnshire Junction Railway and Great Grimsby and Sheffield Junction Railway companies, together forming the Manchester, Sheffield and Lincolnshire Railway in 1847.