The club made the decision following a run of poor form that has seen County win just two of their last 11 outings.
"This obviously is not a decision that we have taken lightly and certainly not one that I have taken any pleasure in reaching, I have a tremendous amount of respect for Keith Curle both as a man and a manager," chairman Ray Trew said in a statement on the club's official website.
"Since Keith first came in, just under a year ago, we, as a Board, have backed him to bring in the players that he believed could move Notts County on to the next level and felt that he assembled a squad capable of challenging for promotion this season.
"However, recent displays have unfortunately not lived up to expectations and our poor disciplinary record this season has only further hampered our progress," he added.
"Attendances at Meadow Lane have dropped in recent weeks and this has made this a business decision as much as a footballing one, because fans are obviously key to the club and their support is essential."
Coaches Colin Lee and Colin West have also been relieved of their duties.