SJ AB
| SJ X 2000 train | |
| Company type | State-owned Aktiebolag | 
|---|---|
| Industry | Rail transport | 
| Predecessor | Swedish State Railways | 
| Founded | 1 January 2001 | 
| Headquarters | , | 
| Area served | 
 | 
| Key people | Monica Lingegård (CEO) Henrik Rättzén (deputy CEO and CFO) Siv Svensson (chairwoman) | 
| Revenue | 7.8 billion SEK (2017) | 
| Owner | Government of Sweden | 
| Number of employees | approx. 4500 (2017) | 
| Subsidiaries | SJ Götalandståg SJ Norge SJ Norrlandståg SJ Öresundståg Stockholmståg | 
| Website | sj.se (Sweden) sj.no (Norway) | 
SJ is the primary passenger train operator in Sweden. A wholly state-owned company operated for-profit under market conditions, SJ operates various services across Sweden. SJ's operations include high-speed trains, intercity trains, night trains, and regional trains, with some services extending into Denmark, Norway and Germany.
SJ traces its roots back to 1856, however was established in its current form as a passenger train operator (SJ AB) in 2001, following the restructuring of Statens Järnvägar, the former government agency responsible for the Swedish railways. SJ AB also has subsidiaries such as SJ Götalandståg, SJ Stockholmståg, and SJ Norge AS, which operate procured regional services in Western Sweden, Stockholm County and Norway, respectively. In 2018, SJ carried 31.8 million passengers.