The Cambridge line runs from Cambridge junction north of Hitchin on the East Coast Main Line to Shepreth Branch Junction south of Cambridge on the West Anglia Main Line and forms part of the route between London King's Cross and East Anglia. The line is part of the Network Rail Strategic Route 5, SRS 05.05 and is classified as a London and South East Commuter line.

The East Coast Main Line (ECML) is a 393-mile long (632 km) electrified railway between its southern terminus at London King's Cross station and Edinburgh Waverley via Peterborough, Doncaster, York, Darlington, Durham and Newcastle. The line is a key transport artery on the eastern side of Great Britain running broadly parallel to the A1 road. The main line acts as a 'spine' for several diverging branches, serving destinations such as Cambridge, Leeds, Hull, Sunderland and Lincoln, all with direct services to London. In addition, a few ECML services extend beyond Edinburgh to serve Glasgow Central, although the principal London-Glasgow route is the West Coast Main Line (WCML).