High-speed rail in Switzerland consists of two new lines and three new base tunnels, including the world's longest railway and deepest traffic tunnel: the Gotthard Base Tunnel whose length is . Each of these tunnels have a technical maximum speed of , which is reduced, at least in the Gotthard Base Tunnel and the Ceneri Base Tunnel, to a maximum authorized speed of , for environmental and economic reasons.
The normal operating speed of passenger trains is limited to , in order to accommodate freight traffic, but in case of delays, speeds up to are possible.
In 1982, the Swiss government, in an effort to increase the effectiveness of their recently introduced regular interval time table, planned and executed the Rail 2000 project in 1987. The first stage of the Rail 2000 project, a route connecting Mattstetten and Rothrist, finished in December of 2004. After the projects completion, the majority of Swiss citizens felt as if their needs were met.
The second stage of Rail 2000, still in project, includes line upgrades in the Valais canton () and between Biel and Solothurn (also ).
New Railway Link through the Alps (NRLA; , , ), is a Swiss construction project for faster north-south rail links across the Swiss Alps. It includes three completed base tunnels several hundred metres below the existing apex tunnels, the Gotthard Base Tunnel, the Lötschberg Base Tunnel, and the Ceneri Base Tunnel. The NRLA also includes the Zimmerberg Base Tunnel for which only Phase I has been completed, in 2003, with an operating speed of , and Phase II remains in project.
NRLA project is building faster north-south tracks across the Swiss Alps by constructing base tunnels several hundred metres below the level of the current tunnels. The Lötschberg Base Tunnel opened in 2007 where New Pendolino trains run. The Gotthard Base Tunnel opened on 1 June 2016. The Ceneri Base Tunnel opened on 4 September 2020.
However, the slow speed of lines between the NRLA tunnels (Ceneri Base Tunnel, Gotthard Base Tunnel and Zimmerberg Base Tunnel to name but a few) means that the capacity of Zürich-Milan services will remain limited until the speeds can be increased, given the strong negative effect of mixed rail speeds on capacity.
The fastest Swiss train is the SBB RABe 501, nicknamed Giruno (Romansh for Buzzard). It is operated by the Swiss Federal Railways since May 2016. It only reaches its maximum speed of in Italy, on the Swiss network it operates at a maximum of .
The French-Swiss co-operation TGV Lyria and German ICE lines extend into Switzerland, the ICE 4 regularly operates at a maximum of (between Olten and Bern), while the TGV never exceeds , due to the lack of a high-speed track between Basel and Zurich.
The former Cisalpino consortium owned by the Swiss Federal Railways and Trenitalia used Pendolino tilting trains on two of its international lines. These trains are now operated by the Swiss Federal Railways and Trenitalia.