The Germany international made the switch to Jurgen Klopp's outfit on a five-year deal in July 2012, after the club agreed a fee reported to be in the region of €17.1 million with Borussia Monchengladbach.
Reus has quickly developed into a pivotal player for Dortmund and the 24-year-old boasts seven goals in 12 Bundesliga appearances this season.
His impressive form has led to rumours of a move to the Premier League, with Manchester United or Arsenal, or Ligue 1 champions Paris Saint-Germain.
Dortmund executive Hans-Joachim Watzke has now confirmed there is a release clause in Reus' contract, with reports suggesting the figure is approximately €35 million.
"Marco Reus possesses a release clause option in his current contract at our club," Watzke told SPORT1media. "He could leave our club due to that.
"He is, however, the only player in our first-team squad that has such a contract clause."
Dortmund's hopes of reclaiming the Bundesliga title from rivals Bayern Munich were damaged by a 2-1 defeat at Wolfsburg on Saturday, which put them four points adrift of Pep Guardiola's table-toppers.
A 1-0 setback at home to Arsenal has also left Dortmund's UEFA Champions League hopes in the balance. They trail Arsene Wenger's men and second-placed Napoli by three points with two Group F fixtures remaining.
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