The Italian was named as coach by the club at the start of the season, but Ajaccio have just one win from 12 matches.
"We have decided to stop our collaboration with Fabrizio Ravanelli and (his assistant) Giampiero Ventrone," Ajaccio president Alain Orsoni told the media.
"This is a decision that was not easy to make from a human point of view. I like these two men, I wanted it to work.
"During my presidency I have never seen staff work so hard, not to mention the hours they put in. They took their task to heart.
"However, I was forced to make a decision in the interests of my position as club president.
"The result (against Valenciennes) has not influenced my choice. This is something that has been thought through and was decided after the defeat to Nantes (on October 19).
"I'm not saying this is necessarily the right solution, only time will tell, but I had to do something."