Ipswich Town have struggled in recent months and suffered a 1-0 home defeat to Nottingham Forest in midweek.
“I can confirm that Ipswich Town football club have amicably terminated the contract of our manager Roy Keane with immediate effect,” Ipswich chief executive Simon Clegg said on Sky Sports News.
“I have to say this is a sad day for Ipswich Town football club and for me personally. I’d like to that Roy Keane for his efforts, his dedication, his support and his professionalism over the last 20 months.
“His reaction to the news is as I would have hoped and expected from someone I’ve got to know over the past two years. One of disappointment and sadness and coupled with the acknowledgment of the opportunity he was given and support he has received.
“We wanted to give Roy Keane the sufficient time to get the team right and to improve the situation. However, as he has said himself, the performances on the pitch since November have simply not been good enough.
“The results speak for themselves. We all carry a degree of responsibility for this failure and I include myself in this. I’m convinced that with a new manager we can achieve the objective and goals we have set for this club.”