Dino Maamria has been named as Oldham's fifth manager in 12 months, replacing Laurent Banide.
Athletic sacked Frenchman Banide – appointed on June 11 but with one League Two win to his name – on Thursday and said an update on a new head coach would be made "soon".
Soon turned out to be 15 minutes, with Maamria, sacked by Stevenage last month, immediately appointed.
"I'm hugely excited to join such an historical football club. The vision and ambition of the chairman was a big factor and the first priority is to stabilise and unite this great football club," he said to Athletic's website.
"I'm here to win football matches as well as improve, give confidence and belief to an already talented squad."
Banide, a former Monaco manager, accrued seven points from a possible 27 during his short time in Lancashire. Assistant Bouziane Benaraibi has also left the club.
"The club would like to thank the head coach and his assistant for their efforts whilst at Boundary Park over the summer and wish them well for the future," a statement read.
Banide took over in the summer after Pete Wild chose to leave. He had replaced Paul Scholes after his short-lived reign, with Wild having served as caretaker prior to that.
Frankie Bunn left Oldham in December last year.
At the time of Banide's appointment, Oldham chairman Abdallah Lemsagam had high hopes for the future, saying "I'm delighted to welcome Laurent to Oldham Athletic.
"He brings a lot of experience to this club and I'm looking forward to working alongside him in the 2019-20 campaign. I believe Laurent is a fantastic coach and is the right man to take this club forward going into the new season."
