Monken, 57, helped Georgia win back-to-back national championships in that role the past two seasons.
He replaces Greg Roman, who resigned from John Harbaugh's staff in January after four seasons as OC and six overall as assistant coach.
The Ravens conducted 21 interviews with 14 candidates before announcing their decision.
"Todd's leadership and coaching acumen were evident from the beginning," Harbaugh said in a statement. "He has a proven track record for designing and teaching offensive systems that allow players to succeed at the highest level. We're excited to get to work and begin building an offense that will help us compete for championships.