Alvia is a high-speed train service in Spain offered by Renfe on long-distance routes with a top speed of 250 km/h (160 mph). The trains have the ability to use both Iberian gauge and standard gauge, which allows them to travel on the recently constructed high-speed lines for part of the journey before switching to the "classic" Iberian gauge network to complete it. Trains that run exclusively on high-speed tracks are branded AVE or Avant.

As of February 2025[update], RENFE Class 120, RENFE Class 130 and RENFE Class 730 trains are in service.
Class 120 trains are used on the routes from Madrid to Pamplona, Logroño, Bilbao, Irún and Hendaye (France) (running on high-speed lines from Madrid to Burgos and changing gauge there), from Madrid to Huelva changing gauge at Seville, from Madrid to Santander changing gauge at Venta de Baños from Madrid to Salamanca changing gauge at Medina del Campo and between Barcelona and San Sebastián, Bilbao (running on high-speed lines between Barcelona and Zaragoza).
Class 130 trains are used on the routes from Madrid to Cádiz, from Madrid to Avilés changing gauge at León, and from Alicante to Gijón and Santander changing gauge at León and Venta de Baños respectively, and between Barcelona and Salamanca/Galicia.
Finally Class 730 are used on the routes from Madrid Chamartín to A Coruña, Ferrol, Vigo, Lugo and Badajoz as well as from Madrid Atocha to Almeria and Algeciras. These trains also used to operate the routes from Madrid to Murcia and further to Cartagena, before those are replaced by AVE Madrid–Murcia services on a new high-speed line. Unlike the other classes, these can run on diesel as well as overhead electric power and so are used on those routes where lines are not electrified.

As of 2024[update] Renfe offers the following Alvia services:
On 24 July 2013, the train driver of an Alvia 730 train traveling from Madrid to Ferrol, Galicia, took a curve well above the posted speed limit and the train derailed near Santiago de Compostela, killing 79 people and injuring more than 140.
On 18 January 2026 an Alvia train crashed into a derailed train in Adamuz, killing 46 people.