Southeastern is a train operating company in the United Kingdom. It began operations in south-east England on 1 April 2006, replacing the former publicly-owned operator South Eastern Trains and serves the commuter routes to south-east London, Kent, and parts of East Sussex. The London termini of its services are Charing Cross, Blackfriars, Cannon Street, and Victoria. Southeastern operate on 773 miles (1237 km) of track, with 182 stations. 82% of its train services run into London.
It is owned by Govia, which is itself jointly owned by Go-Ahead Group and Keolis, who also operate the neighbouring Southern operating company which overlaps with Southeastern in some areas. The company's formal name, under which it mounted its bid for the franchise, is London and South Eastern Railway. Although it continued to use the logo and livery of its predecessor for its first year of operations, a new company logo was adopted early in 2007 and stations, beginning with Waterloo East, have begun to be re-painted under the new corporate colour scheme. In August 2007, a Class 508 train was painted in a new trial livery, although the company has stated that the exact design is yet to be finalised.

Current routes
From London termini (Victoria, London Bridge, Waterloo East, Charing Cross, Blackfriars, and Cannon Street) unless otherwise stated;

North Kent Line: services via Dartford to Gillingham
Chatham Main Line - services to the Kent Coast via Bromley South and Chatham, dividing at Faversham to Ramsgate and Dover
Swanley to Ashford (via Maidstone East) Line
South Eastern Main Line - services the Kent Coast via Ashford and Sevenoaks

• Ashford to Ramsgate (via Canterbury West) line
  Kent Coast Line: Ashford to Ramsgate (via Folkestone and Dover)
  Hastings Line (Hastings via Tunbridge Wells)
  London Bridge to Tunbridge Wells (via Redhill and East Croydon) — uses part of the Brighton Main Line Main lines
  The suburban services run to:
  
  Sevenoaks: two services — one via Grove Park to Charing Cross, and one via Swanley and Bromley South to Blackfriars (Catford Loop Line).
  Hayes line to Charing Cross
  Orpington
  
  
  
  • via Lewisham to Charing Cross (South Eastern Main Line)
    via Bromley South to Victoria (Chatham Main Line)
    Dartford via: North Kent Line, the Bexleyheath Line, and the Dartford Loop Line to Charing Cross.
    Bromley North Line Suburban lines
    
    Medway Valley Line, some services extend to Tunbridge Wells, and occasionally to Gatwick Airport and Three Bridges
    Sheerness Line
    Horsham to Tunbridge Wells (via Gatwick and Redhill) — uses part of the Brighton Main Line and Redhill to Tonbridge Line (to be transferred to Southern during 2009). Rural lines
    
    Future expansion
    Following the completion of the Channel Tunnel Rail Link (also known as "High-Speed 1" or HS1), Southeastern will operate high-speed domestic services on it, including the Olympic Javelin service that is to run during London's 2012 Summer Olympics.
    A fleet of twenty-nine six-carriage Shinkansen-derived high-speed 'A-trains' have already been ordered from Hitachi for this route.
    
    CTRL-DS and Olympic Javelin
    Due to the opening of the second phase of the CTRL in November 2007, improvments to the services provided are scheduled to begin from December 2007, due to train paths becoming available.
    
    An additional evening peak train from Charing Cross to Tunbridge Wells;
    An additional evening service from Cannon Street to Faversham with connections to the Thanet coast;
    Improved frequency of services between Beckenham Junction and Victoria and Orpington and Victoria, improving links to Bromley South;
    Contra peak improvements on many Metro routes and on the main line via Tonbridge; and
    Improvements made to Saturday services so they mirror, where possible, the Monday to Friday off peak pattern "Traditional" network
    Like its sister franchise Southern, Southeastern is committed to introducing Oyster Pay As You Go (PAYG) on its London routes but is yet to implement.
    
    Ticketing
    Southeastern operate a fleet of about four hundred trains, all of which are electrical multiple units.
    
    Rolling stock
    
    Future fleet
    
    Olympic Javelin
    South Eastern Trains
    Connex South Eastern
    Network SouthEast
    Southern Region of British Railways
    Southern Railway
    South Eastern and Chatham Railway
    South Eastern Railway
    London, Chatham and Dover Railway