Southeastern (train operating company, 2006–2021)

Southeastern was a train operating company in the United Kingdom that operated the South Eastern franchise from April 1, 2006, to October 16, 2021. The franchise covered passenger rail services in South East England, including commuter services into London from Kent and East Sussex.

Southeastern's routes primarily served London Charing Cross, London Victoria, London Cannon Street, and London St Pancras International (domestic high-speed services). The company operated a mix of high-speed services (branded as Southeastern Highspeed, using Class 395 trains on High Speed 1) and metro services.

The company was owned by Govia, a joint venture between Go-Ahead Group (65%) and Keolis (35%).

In June 2021, the Department for Transport (DfT) announced that Southeastern would be taken over by the government from October 17, 2021, following a Serious Fraud Office investigation into financial irregularities relating to over £25 million of taxpayer funding. The DfT stated that Southeastern had failed to declare significant revenue and that this revenue should have been returned to the government. Following the termination of Govia's contract, the operation of Southeastern services was taken over by a new operator of last resort, also named Southeastern, but publicly owned and operated by the DfT. This new entity commenced operations on October 17, 2021, and continues to operate the South Eastern franchise.