In Sweden many trains run at . Train types which currently attain this speed include the X 2000 tilting trains for long distances, the Regina widebody trains, the X40 double-decker regional trains, the Arlanda Airport Express X3, the MTRX-trains, FlixTrains and the Stadler KISS-inspired double-decker regional trains. Since both the X2 and X3 are allowed to run at in case of delay, they can technically be considered as high-speed trains. The X2 runs between many cities in Sweden including Stockholm, Gothenburg, and Malmö. The Arlanda Express trains connect Stockholm and Stockholm-Arlanda Airport.
Current plans
Upgrades to existing lines
Hundreds of kilometers of track are ready for operation, with the exception of signaling systems, catenary, and the trains themselves. A modified Regina test train, called "the Green Train", has attained a maximum speed of , with regular service at planned.
There are plans for a section of the Stockholm-Malmö line to be upgraded to allow for speeds of . These plans have been delayed until further notice because a decision must be made regarding whether to build a new parallel super-high-speed railway or not. Other railways that will eventually allow speeds (today ) are long sections of Stockholm–Gothenburg, Gothenburg–Malmö, and Trollhättan–Gothenburg. A new Kramfors–Umeå line, Botniabanan has been ready for non-tilting trains since 2010, but train operators have not yet revealed plans for trains on Botniabanan, or on any other capable line. All these will be mixed passenger/freight railways.
The Swedish signalling system ATC does not currently allow for higher speeds than , and current plans allow for higher speeds only with a future EU-system called ERTMS. Botniabanan has had this system in operation since 2010, allowing . ERTMS will be introduced on certain other railways around 2015, possibly enabling more than on them. The ATC does in theory allow but that would require reinstalling most track equipment and signals since ATC uses point based transmission, and higher speed means new points of transmission. ATC is installed for along east of Södertälje but no trains are approved for that.
SJ have bought new trains (type X55, delivered 2010) that are prepared for but limited to until a later date.
Due to worsening condition of tracks, since 2017-18 trains should slow-down from on some stretches. For instance, Stockholm to Malmö service now is going for 4.5 hours, which is 30 minutes longer than previously, reaching an old level of year 1991.
New lines
There were plans for completely new high-speed railways Stockholm–Linköping–Jönköping–Borås–Gothenburg ("Götalandsbanan") and Jönköping–Helsingborg–Copenhagen ("Europabanan" for the Swedish part), since the existing railways are relatively congested, with mixed passenger trains, slower regional trains and even slower cargo trains. The plans said that the new railways would be built similar to the French TGV-lines with long curve radii and relatively steep inclines allowing for speeds between with non-tilting trains, dedicated for high-speed passenger trains.
The Swedish Transport Administration (Trafikverket) started detailed planning and was in the process of deciding the best route between Gothenburg–Borås and Linköping–Södertälje (Ostlänken), however no specific dates have been determined for the start of construction on these lines. An informal proposal by Trafikverket is an operational track by 2025. There is political and (primarily) regional pressure to build these railways as soon as possible. Cost estimates are about 10 bn SEK for Gothenburg-Borås and 24 bn SEK for Linköping-Södertälje.
In 2018 Chinese corporations became interested in building of Stockholm-Oslo high-speed line. Trafikverket awarded American engineering firm Jacobs Engineering Group with the contract to consult on a proposed $24 billion high-speed rail network linking Stockholm with Gothenburg and Malmö.
In late 2022, the then newly elected centre-right Swedish government decided to completely abandon Sweden's high-speed rail project.
New trainsets
In December 2021, SJ has announced that they are ordering 25 trainsets (Zefiro Express) which are capable of going . They are expected to go into service in 2026, and will also be used for cross-border traffic with Denmark and Norway.