Goal exclusively revealed in October that Manchester City are ready to step up their long-standing interest in Reus, with Dortmund manager Jurgen Kloop recently admitting the 25-year-old could leave the club.
Reus, who was recently ruled out for the remainder of 2014 through injury, has a buyout clause in his contract which becomes active in the summer, prompting links with Bayern Munich and Real Madrid.
When asked if Chelsea are keen on Reus, Mourinho told reporters: "We are not interested, not at all."
Mourinho was speaking to the media ahead of Chelsea's Champions League trip to Schalke as they look to take another step towards reaching the knockout stage against former manager Roberto Di Matteo.
"We need points to continue playing in the Champions League this season, and that is why we are here, to win," he added.
"We have two matches left to make the next stage, but it will be better to qualify tomorrow, so many matches in December."