Winless Le Havre sit bottom of Ligue 1, on just two points, and Friday's humbling defeat by PSG was the tipping point for the club's American owners, Blue Crow Sports Group.
In a statement, the owners said they had "accepted the principle of Mr Jean-Michel Roussier's resignation from his position as chairman".
That resignation will be formalised at a board of directors meeting on Thursday.
"Furthermore, Le Havre Athletic Club has notified its coach, Didier Digard, of his precautionary suspension pending further decisions within the framework of ongoing proceedings," they added.
The club has appointed Jair Karam, the youth teams director, as interim coach to take charge of the first team from Monday for the resumption of training.
Digard is the second coach sacked so far this season after Lens fired German coach Dino Toppmoller after just six league games in charge.