REFER, Rede Ferroviária Nacional, EP (i.e. National Railway Network) was the Portuguese rail infrastructure manager.

It was a state-owned company and was created to manage the Portuguese rail infrastructure, previously under control of CP, which became exclusively a train service operator.

The Linha do Sul, at 274 km was the principal main line in the south of the country, but it terminated short of Lisbon on the south side of the river Tagus (Tejo in Portuguese) but it received a considerable improvement when it was extended from Pinhal Novo to Lisbon over the Ponte 25 de Abril, which was provided with an additional railway deck.

The earliest railways in Portugal were built to standard gauge (1,435 mm) but were regauged in the nineteenth century for compatibility with the trains of the railways of Spain, which at that time used a track gauge of 1,668 mm.

These were to be built in standard gauge to allow easy connection with the Spanish high speed network but most have since been downgraded.