A train operating company (TOC) is the term used on the railway system of Great Britain for a railway undertaking operating passenger trains under the collective National Rail brand. TOCs have existed since the privatisation of the network under the Railways Act 1993.
There are two types of TOC: most hold franchises let by the Department for Transport (DfT) through a tendering system, to operate services on certain routes for a specified duration, while a small number of open-access operators hold licences to provide supplementary services on chosen routes. These operators can run services for the duration of the licence validity. The franchised operators have changed considerably since privatisation: previous franchises have been divided, merged, re-let to new operators, or renamed. Some privately-operated franchises have been taken over by a government-owned operator of last resort, due either to failing expectations or to events on the rail system as a whole.
The term is also sometimes used to describe companies operating passenger or freight rail services over tracks owned by another company or a national network owner.