22-year-old Baku, who is capable of playing in defence or midfield, has put pen to paper on a five-year deal.
— VfL Wolfsburg (@VfL_Wolfsburg) October 1, 2020
A Germany under-21 international, Baku has impressed with his performances in recent years.
His form caught the eye of several clubs, including French giants Paris Saint-Germain who considered him.
However, Baku will remain in the Bundesliga and wear the number 20 shirt at Wolfsburg.
“I’m looking forward to the new challenge,” said Baku upon signing. “I have everything to thank FSV Mainz 05 for and the club will always have a special place in my heart.
“However, I felt it was time to take the next step in my development and in Wolfsburg I have the best conditions to do that.”