The Ypres sector of the Western Front was held predominantly by the British and Dominions Armies from 1914 to 1918. The Ypres Salient, at the centre of this sector, was one of the most intensively fought over single locations of the First World War. By the end of 1917 the sector was full of railways, dumps, camps, and other facilities. Much was lost in the German advance in April 1918, but from September 1918 the German Army was driven eastwards until the Armistice. Although Ypres and most of the forward areas are in Belgium, much of the support area is in northern France. In this book the metre gauge networks of both countries established before the First World War are examined, with their uses and extensions during the War. The build up of light (60cm gauge) railways from 1916 to 1918 is described, with an assessment of the contribution of both narrow gauges to the war effort. After the war the light railways in this sector were generally used only for short term clearing up and salvage. The metre gauge railways in Belgium were rebuilt or repaired. Those in France had been less affected. The story is followed to the closure of the last of these railways. This book is a companion volume to those on the Arras Sector (2015), and the Somme Sector (2018). It refers to other previous works on British, French and Belgian railways, especially during the First World War, but contains sufficient information to stand alone.