The 43-year-old takes charge of the Championship's bottom club five months after he left Celtic, where he won three Scottish league titles in four years.
"The club are delighted and excited to appoint Neil Lennon," read a statement on their website this afternoon. "He brings with him experience at the highest level and an infectious enthusiasm to take the club forward."
The Northern Irishman's first game in charge will be a trip to Birmingham City on Saturday afternoon. The Trotters then go to Charlton Athletic on Tuesday, October 21 before his first home game against Brentford on Saturday, October 25.