Borrussia Dortmund announced the Germany Under-21 international midfielder’s signing on Wednesday, with Philipp having agreed a five-year contract for Peter Bosz’s side.
The 23-year-old played 25 times for seventh-placed Freiburg in last season’s Bundesliga, scoring nine goals including one in a 3-1 away defeat to Dortmund in September.
“BVB are one of the biggest clubs in the world. It is an honour for me to be able to play here,” Philipp told the club’s website.
“I think that at 23 I am mature and old enough to be able to take this step. Now I want to develop further at Dortmund.”
Philipp will represent Germany at the Under-21 Euros and then take a three-week break before joining up with his new team-mates.