Rudi Garcia admits it was a wrench to leave Le Mans, but he could not refuse a return to Lille.
Following Claude Puel's appointment as the new Lyon coach, Lille have brought in Garcia as his replacement.
Garcia was a former Lille player and is looking forward to his return to the club, but also acknowledged his sadness at moving on from Le Mans.
"It has been a heartbreak to leave Le Mans and their chairman," Garcia told a news conference.
"But when Lille contacted me, I didn't hesitate. It is just like coming back to my family and I am ambitious."
Lille are now turning their attentions towards player recruitment and the permanent signing of Rio Mavuba is a priority.
Mavuba spent the second half of last season on loan at Lille from Villarreal and the midfielder is nearing a return.
"We have concluded a financial agreement with Villarreal for the transfer of Rio Mavuba," said Lille president Michel Seydoux.
"It is not done yet, but it is going well."