League 1 Oldham Athletic sack manager after just four months
The 36-year-old took charge of just eight matches after being appointed in May on a two-year contract.
Former Sunderland coach Kelly was dismissed following Saturday's 5-1 home defeat by managerless Peterborough.
Oldham, who have won only one of their seven league games this term and are 19th in the table, say they will "not be seeking applications" for the role.
A club statement added that all of the current coaching staff will remain in their respective roles.