Huddersfield are the seventh League One side to change manager this season.
Grant’s dismissal means that Carlos Corberan in 2021-22 remains the last Terriers boss to lead the club for a whole season.
Since the Spaniard’s exit, seven managers have now come and gone in West Yorkshire.
Grant arrived at Huddersfield in the summer after three years on Kieran McKenna’s coaching staff at Ipswich.
The former Derby, Burnley, Sheffield Wednesday and Stoke goalkeeper reshaped a squad which had laboured to a 10th-place finish last season.
Birmingham striker Alfie May was signed for in excess of £1m and experienced Championship players Jack Whatmough, Ryan Ledson and Lynden Gooch were also brought in.
That recruitment drive and the ambitions of American owner Nagle saw the club backed as pre-season favourites for promotion and they started the campaign in style with a 3-0 home win over last season’s beaten play-off finalists Leyton Orient.
They were third when they travelled to local rivals Bradford City on 13 September but slumped to a 3-1 defeat at Valley Parade and have not climbed that high since.
Although they have spent the majority of the season in or just outside the top six they are now 16 points behind leaders Cardiff, having played a game more.
They host the third-placed Bantams next Saturday looking to end a four-match winless run.
