It runs from the Brighton Main Line at South Croydon in Greater London to Hurst Green Junction in Surrey, where its two branches diverge.

Services operated by Class 377 electric multiple units generally call at all stations between Sanderstead and East Grinstead; services operated by Class 171 diesel multiple units call at all stations between Oxted and Uckfield, but generally run non-stop between East Croydon and Oxted.

The first part of the route to be completed, between Eridge and Uckfield, was opened by the London, Brighton and South Coast Railway (LB&SCR) in August 1868.

The new link not only enabled trains from east Kent to reach Brighton, but was also intended to block a rival scheme from the London, Chatham and Dover Railway, which would have followed a similar route.

Work began the following year, but progress was slow due to the financial panic of 1866 caused by the failure of Overend, Gurney and Company.

By the time the works were halted, the viaduct at Woldingham had been completed and substantial progress had been made on the tunnels at Riddlesdown, Oxted and Limpsfield.

The line was to use the partially built track bed as far south as Limpsfield Tunnel, from where it would continue to meet the Lewes and East Grinstead Railway, authorised the previous August.

[56] Under the terms of their ownership agreement, the SER was responsible for providing stations at Upper Warlingham and Oxted, while the LB&SCR built those at Lingfield and Dormans.

[56] Three years later, under the London, Brighton and South Coast Railway (Various Powers) Act 1884, the LB&SCR was authorised to acquire the O&GR.

[58] As part of the works, a single track link, known as the Withyham Spur, was constructed to allow trains from Oxted to access Uckfield without a reversal at Groombridge.

[68] Development at Dormans Park began in 1887 and, by 1891, a hotel and around 40 high-class "bungalow residences" had been built, set in grounds that included cricket and polo fields, a golf course and a fishing lake.

[28][77] Shortly before the start of the First World War, the Withyham spur was doubled, allowing regular passenger services from Uckfield to reach London via Oxted.

[79] The first proposals to electrify the route, using overhead lines energised to 1,500 V DC, were put forward by the LB&SCR in the late 1910s and early 1920s.

In mid-1955, the railway between East Grinstead and Lewes was shut, but following legal action it temporarily reopened in August the following year, before permanently closing on 17 March 1958.

[98][99][d] The withdrawal of passenger services on the line between Eridge and Tunbridge Wells was announced in September 1982, although trains continued to operate until 6 July 1985.

[103] From 1982, the railways in Surrey, Kent and Sussex came under the control of the London and South East sector of BR, which was rebranded to Network SouthEast in June 1986.

[104][105][106] As part of an initiative to provide passenger routes with individual identities, Nework SouthEast introduced the name "Oxted Line" in 1989.

[61][83] In March 1983, third-rail electrification between South Croydon and Sanderstead was commissioned and electric trains began running on this short section of the Oxted line in May of that year.

[20] A new station building for Oxted line trains at East Grinstead was first used by the public in December 2012 and was officially opened on 8 March the following year.

[138] In the early 1950s, Fairburn 2-6-4T tank engines were introduced to the Oxted line, but were criticised by railway staff for being underpowered for the steep gradients.

[138][139] Class 207 diesel multiple units began working on the Oxted line on 18 June 1962, initially operating the busiest passenger services during peak hours.

[61][144] Passenger numbers increased as a result of the electrification and Class 415 "4-EPB" units, with standard class-only seating, were introduced in late 1988 to provide additional capacity at peak times.

From 1886, a standard-gauge, single-track branch ran from the Oxted line to three sidings at the base of the quarry, where lime could be transferred from the internal 2 ft (610 mm) system.

[160] The goods yard at Woldingham shut on 4 May 1959[161] and those at the south end of Mark Beech Tunnel, at Cowden and at Ashurst closed the following year.

[160] Electrification of the Hurst Green Junction–Uckfield section of the Oxted line, currently operated by Class 171 diesel multiple units, was identified as a priority by Network Rail in 2022.

[14][165] The "East Sussex Rail Strategy and Action Plan", published in November 2013, favoured electrification as well as redoubling the single-line sections.

It suggested that these infrastructure improvements would reduce journey times and allow a more efficient use of rolling stock, which could lead to an increase in service frequencies.

[170][171][172] Although the track bed has been protected from development since May 1980,[173] the rail infrastructure operators and the British government have repeatedly refused to authorise the schemes.

[174][175][176] The report published by Chris Gibb in March 2017 indicated that there would be no business case for rebuilding the Uckfield–Lewes line unless there was strong housing growth in the area.

Furthermore, Gibb suggested that works to increase the capacity of the Brighton Main Line should be prioritised ahead of the construction of a new high-speed link.