Owners Fawaz Al Hasawi and Abdulaziz Al Hasawi have made the decision as they look to move the Club forward.
Chairman Fawaz Al Hasawi said: “We cannot speak highly enough of Sean as a man. He was appointed at an extremely difficult time for the Club and can count himself unlucky to have lost his job with the team just one point away from the top six.
“But we have a responsibility to look to the future for this great Club because we have huge ambitions for it.
“We knew when we bought the Club in the summer that it would take time for the players we bought in to settle but that process has taken longer than we anticipated.
“We feel we have developed a really strong squad of players but are still searching for consistency in terms of team performance, underlined by the fact that we have not won more than two games in succession in the Championship this season.
“And with the January transfer window approaching, we feel it’s the right time to make a change.
“We are looking to bring in an ambitious manager with Premier League experience.”
Abdulaziz Al Hasawi, who was at The City Ground for today’s game against Leeds, added: “The timing of our decision may look a little odd after the win over Leeds but sometimes you need to make changes with the long term future in mind.
“Sometimes those changes need to be made from a position of strength rather than weakness and that is what we are trying to do.”
The Club will be making no further comment at this time.