Statens Jarnvagar (SJ) operate the national rail service, throughout Sweden, including cross-border trains from Stockholm to Oslo (Norway) and from Stockholm to Narvik (Norway) in the far north; this service, while entering Norway is operated entirely by SJ. You can use the SJ online timetable to plan your trip as you go through the ticket purchasing process. PDF downloads are available for all SJ Routes in Sweden.
A comprehensive list of both passenger and freight operators in Sweden can be found on the helpful Railfan Europe website’s Sweden page.
Train times and Tickets
Booking tickets for travel within Sweden can be done at stations. Tickets are also available online, information regarding the ticket types, validity and periods available is here. If you only require reservations for either Interrail, Eurail these can actually be done on the SJ website by selecting Inter/EU Rail seat reservation under the Customer Card heading in the Traveller Information section.
If choosing to use an Interrail pass, either for just within Sweden, or to pass through Sweden, all the relevant details on the passes, including the different types/lengths of validity available, can be found on the InterRail website.
Finally travel in Europe can be made a lot simpler by using the very, very, helpful smartphone app courtesy of Eurail. This app is available both online and offline and is always up to date (well it has been for the countries I’ve used it in; including for any planned engineering works); for me it was an essential part of my travel in Europe. This app is linked to the Hafas system, which countries like Germany, Austria & Switzerland use for their train planning online tool. Eurail has done what the individual countries haven’t though and made it available offline.
For the Rail Enthusiast
A comprehensive list of Swedish Locomotives by their respective railway system can be found on the Railfaneurope website’s Sweden page. This also explains a bit the various operators of the network and how they have amalgamated over the years.
A detailed map/atlas of the Nordic Railway Systems, which includes Sweden, is available from European Railway Atlas.