Carolus Rex is the sixth studio album by the Swedish power metal band Sabaton. It is a concept album based on the rise and fall of the Swedish Empire, whose monarch Charles XII gives it its title. It was released with both English and Swedish vocals. It is the last album to feature guitarists Oskar Montelius and Rikard Sundén, drummer Daniel Mullback and keyboardist Daniel Mÿhr. It was produced by Peter Tägtgren in Abyss Studios. The album received critical acclaim and commercial success, achieving gold certification in Poland and quadruple platinum in Sweden.
In 2015, four Carolus Rex songs were featured in the Sabaton Soundtrack DLC for the historical grand strategy game Europa Universalis 4 by Paradox Interactive. The four included with the DLC were "The Lion from the North", "A Lifetime of War", "The Carolean's Prayer", and "Carolus Rex". Another song ("The Art of War") from Sabaton's The Art of War album was also included.
As of 18 September 2012, the album is certified gold in Sweden, selling over 30,000 copies (20,000 copies sold is needed for an album to be certified gold in Sweden). As of March 2013, the album is also certified gold in Poland. On 18 June 2013, Carolus Rex was certified platinum in Sweden with 40,000 album sales, making it the "most successful Swedish heavy metal album ever" according to the band.
On 28 September 2018, Sabaton announced that the album had been awarded quadruple platinum status after remaining on the Swedish chart for 326 weeks, and commemorated this with a number of limited edition versions and merchandise. These were set for release on 30 November 2018, the 300th anniversary of the death of Charles XII.
In 2019, Metal Hammer ranked it as the 20th best power metal album of all time.
A Swedish language edition of the album is also available.
The limited 2-CD mail order edition of the album includes the English version with all of the bonus tracks and the Swedish version, as well as alternate artwork.