He was an ever-present for Freiburg last season and departs with an overall record of 70 Bundesliga games and two goals for the club.
In both 2012 and 2013 he was named Germany's best player in his age group, winning the Fritz-Walter-Medaile.
It is reported that the fee for Ginter is around £8 million.
"For me, today is a childhood dream come true," said Ginter. "I was always a great BVB fan and will now wear the jersey of my favourite team.
"At Dortmund, I would like to take the next step in my sporting development. I am already looking forward to the incredible atmosphere at Signal Iduna Park and then be part of this wonderful team,"
- Sports & Recreation