Ajaccio fired Dupont on Monday, with club chairman Alain Orsoni saying the relationship between the players and their coach had deteriorated.
"Official, Albert Emon will be Ajaccio's new coach from January 2, 2013," the club said in a statement on their website.
Emon, 59, had two short spells at Marseille, leading them to the second spot in 2007 in his only full season in charge. He also coached top-flight side Nice in the 1990s.
The Corsican team are 14th in the table, three points out of the relegation zone. They host sixth-placed Stade Rennes on Saturday for their last match before the winter break.