The raven-haired beauty - a former Swedish reality TV star and model - has apparently moved in with the dashing royal.
According to the Swedish press, 25-year-old Sofia in now ensconced in Carl's apartment, close to the royal palace in Stockholm.
And although she is officially listed as living with her parents Erik and Marie in Alvdalen, to the north of the city, she actually spends all of her time at Carl's residence, reports Swedish magazineSvensk Damtidning.
The couple have been dating since January, following Carl's split from his long term girlfriend Emma Pernauld in March 2009.
In July this year the Palace confirmed Carl's new romance after moving to block the publication of naked pictures of Sofia.
Now living together, the couple are apparently making some changes to the décor of Carl's apartment to reflect Sofia's tastes. The prince has been spotted shopping in IKEA.
A source told the press: "Sofia wants nothing to do with any of Emma's things, so some changes were absolutely necessary."