"Mike is an excellent defensive mind who is highly respected across the NFL. He has been a valuable member of the Baltimore Ravens staff, and shown a passion for teaching, coaching, and developing his players," head coach Jim Harbaugh said.
Macdonald will replace Don Brown, who was dismissed after five years in Ann Arbor.
The assistant just finished his seventh season with the Ravens, and third as the team's linebackers coach. He previously spent time as Baltimore's defensive backs coach (2017) and as a defensive assistant (2015-16).
Brown usually fielded a strong defensive unit, but the Wolverines declined in 2020. The group ranked 11th in 2019, then fell to 87th this past campaign while allowing 434 yards per game.
Michigan recently rewarded head coach Harbaugh with a five-year contract extension.