The British Transport Police (BTP; Welsh: Heddlu Trafnidiaeth Prydeinig) is a national special police force that polices the railway network of Great Britain (England and Wales, and Scotland), which consists of over 10,000 miles of track and 3,000 stations and depots.

BTP also polices the London Underground, Docklands Light Railway, West Midlands Metro, London Tramlink, part of the Tyne and Wear Metro, Glasgow Subway and the London Cable Car and provides the 61016 text messaging service for passengers to report non-emergency crimes and incidents.

The force is funded primarily by the rail industry.

As well as having jurisdiction across the national rail network, the BTP is also responsible for policing:

This amounts to around 10,000 miles (16,000 km) of track and more than 3,000 railway stations and depots. There are more than one billion passenger journeys annually on the main lines alone. BTP do not police heritage railways in Britain.

In addition, BTP, in conjunction with the French National Police (under the Border Police unit) – Police aux Frontières – police the international services operated by Eurostar.

A BTP constable can act as a police constable outside their normal railway jurisdiction in certain circumstances described in the "Powers and status of officers" section.

BTP constables previously had jurisdiction at docks, ports, harbours and inland waterways, as well at some bus stations and British Transport Hotels. These roles and powers were phased out in 1985 with railway privatisation. The legislation was amended to reflect this in 1994.