The 20-year-old centre-back has penned a five-year contract with the Westphalians, the club he always adored.
'The next step'
"Today, I'm fulfilling a childhood dream," he said. "I was always a huge Dortmund fan and now I'm getting the chance to wear the shirt of my favourite club. I'd like to take the next step of my development in Dortmund and I'm already looking forward to the amazing atmosphere in the Signal Iduna Park and being able to be part of this wonderful team that I've only seen and heard positive things about."
Ginter will report for pre-season training under the orders of head coach Jürgen Klopp at the start of August together with fellow world champions Roman Weidenfeller, Erik Durm and Kevin Großkreutz.
More options for Klopp
With Ginter new in the squad Klopp will then be able to rely on an extra defender after injury problems last season saw his options reduced in that department. "We're playing in three competitions, are very ambitious and have made a conscious decision to go into the season with four strong central defenders," said Dortmund's sporting director Michael Zorc.
"Matthias is a technically strong and versatile top German talent who has always enjoyed a high degree of interest from us. We're pleased and also a bit proud that he expressed his desire to join Dortmund so soon and so emphatically," Zorc added.
Ginter made a total of 81 Bundesliga appearances for Freiburg, scoring five goals. He has been capped by Germany three times.