Former world No. 6 Monfils officially retired last month after bowing out in the US Open's second round in September, ending a 22-year professional career that included two Grand Slam semi-final appearances.
But Monfils is set to be at the courtside when France begin their Davis Cup qualifying campaign in February, after he took over the captaincy from Paul-Henri Mathieu, who led them to the quarter-finals last year.
"I am immensely proud to become captain of the French team. This blue jersey means so much to me," Monfils said in a statement.
The 40-year-old represented France in eight editions of the Davis Cup, and won 12 of his 15 singles matches. He delivered one of his best performances in the 2014 final, beating Roger Federer in straight sets, although France lost the tie to Switzerland.
Monfils was not in the team when France won their 10th Davis Cup title in 2017, but said he was keen to add to their trophy cabinet as captain, a non-playing role.
"I want to build a genuine team-based project and create the momentum that will enable us to win titles together," he added.