Created on January 1, 2005, through the division of the historic state railway RENFE (separating rolling stock operations from infrastructure management to comply with European Union railway directives), Adif is the state-owned rail infrastructure manager of Spain. In 2013, the organization was structurally bifurcated into two coordinated state entities: Adif (managing conventional 1,668 mm Iberian-gauge and 1,000 mm metric-gauge networks, stations, and freight logistics terminals) and Adif-Alta Velocidad (Adif AV, dedicated to the financing, construction, maintenance, and operation of 1,435 mm standard-gauge high-speed lines).

Operating under the Ministry of Transport and Sustainable Mobility, Adif manages a comprehensive national network exceeding 15,000 track kilometers, including over 4,000 kilometers of high-speed passenger corridors—the longest high-speed network in Europe and the second-largest globally after China. Adif AV led the technical harmonization and liberalized open-access commercial rollout across the network, facilitating competitive multi-operator high-speed services between Renfe (AVE/Avlo), SNCF (Ouigo España), and ILSA (iryo).

Adif leads major engineering feats across extreme mountainous topographies, including the 25-kilometer Pajares Base Tunnel beneath the Cantabrian Mountains, extensive dual-gauge (Iberian and standard gauge via three-rail tracks) transitions, automated gauge-change facilities (cambiadores de ancho), and nationwide implementation of ERTMS/ETCS Level 1 and Level 2 signaling combined with ASFA Digital train protection.