This list is for railway lines across Great Britain and Northern Ireland, which are now abandoned, closed, dismantled or disused.
Within the United Kingdom, examples exist of opened railways which formerly constituted cross-country main trunk lines as well as many more which served more local, or exclusively industrial, needs.
Some of the included lines have re-opened, in part or in full, following a period of closure.
Such reopenings have taken the form of independent preserved heritage railways, and of expansions to state-backed National Rail and local rapid transit/light rail networks.
Bicester to Bletchley section to be reopened (under construction as of April 2023) as East West Rail.