The Leen Valley lines of the Great Northern Railway were railway branch lines built to access the collieries in the Nottinghamshire coalfield in England. The Midland Railway had long been dominant in the area, but there was resentment against its monopolistic policies from coalowners, who encouraged the Great Northern Railway to build a line. The Leen Valley Line was opened in 1881; it ran as far as Annesley colliery. A passenger service was run the following year, and very considerable volumes of coal were hauled.
Coal owners in areas further north made representations to the Great Northern Railway, which agreed to extend the line, and the Leen Valley Extension Line opened in 1892. The Manchester, Sheffield and Lincolnshire Railway had built a line on a nearby alignment including a long tunnel, and to avoid the cost of duplicating the tunnel, the GNR arranged to use the MS&LR tunnel to connect its Extension line to the original section. At its northern extremity, the line connected to the Lancashire, Derbyshire and East Coast Railway at Shirebrook. A passenger operation was worked on the Extension line too, but again coal traffic was massively dominant. In fact the passenger service was discontinued in 1931.
In the 1960s and 1970s coal production in the area declined steeply, and the duplication of railway routes in the area meant that rationalisation was inevitable: it was the former GNR lines that bore the brunt of this. In the 1980s plans were formulated to reopen a passenger train service from Nottingham to Mansfield; this was to be mainly on the former Midland Railway route, but a short section of the former GNR line was used around Kirkby-in-Ashfield. The new service and route, marketed as the Robin Hood Line, was opened progressively from 1995 onwards.