Ipswich have sacked manager Paul Cook following Saturday's FA Cup second-round goalless draw at home to Barrow.
The former Accrington, Chesterfield, Portsmouth and Wigan boss, 54, only took over the League One side in March.
Ipswich chief executive Mark Ashton said: "Following discussions with the board, we have decided a change is needed for our long-term interests.
"I know how much Paul wanted to succeed at this club. At this moment, there is no one lined up to replace him."
Former English top flight side Ipswich will now be seeking their fourth manager since Mick McCarthy left in April 2018, following the short reign of Paul Hurst and two-and-a-half years of Paul Lambert.
Cook was appointed on 2 March, just a month before long-time Ipswich owner Marcus Evans sold the club to American investment fund ORG.
"We would like to thank Paul and his team for their efforts in what has been a difficult transition period for everyone," added Ashton. "There will be an extensive search to find the best replacement.
"I will communicate more to the media and our supporters on Monday."
Ipswich lie 11th in League One, 11 points and nine places behind Cook's previous club Wigan, who he left at the height of their financial troubles, after three years in charge.
