Lennon returns to management five months after he left Celtic, where he won three consecutive Scottish league titles.
"This is a huge challenge and that is what I was looking for," Lennon told a press conference this afternoon.
"Things went really well at Celtic but it was time for a change."
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.