The Dartford Loop Line is one of three lines linking London with Dartford in Kent, England. It lies to the south of the other two: the North Kent Line and the Bexleyheath Line. It was opened by the South Eastern Railway on 1 September 1866: because there are no major engineering works on the route it took a mere four years to build. It was electrified with the other two routes on 6 June 1926.

The line is a little over 9 miles (14km) in length: the following are the stations served:

• Hither Green - the station lies on the main line from London to Kent: there are separate platforms for the Loop Line
  • here there is a triangular junction for freight traffic going to the extensive Hither Green freight sidings
• Lee
• Mottingham - named Eltham until 1927
• New Eltham - built in 1878 to serve a growing suburban area; originally named Pope Street
• Sidcup
• Albany Park - opened 7 Jul 1935 to serve a new housing development
• Bexley
• Crayford
  • here there is a triangular junction with the North Kent Line providing access to the Slade Green carriage sidings and to Dartford.

Trains run from London (Charing Cross and/or Cannon Street): most terminate at Dartford, although two trains an hour serve the line to Gravesend also.