The 36-year-old manager led Swansea to an eighth-place finish last season but has paid the ultimate price for the club’s woeful performance in the English Premier League this season, which has left Swansea with just a point above the relegation zone.
The club chairman Huw Jenkins in a statement said: “The decision has been made very reluctantly and with a heavy heart.”
“To find ourselves in our current situation from where we were in the first week of September, and considering the drop of performance levels and run of results over the last three months, it has brought us to this unfortunate decision today.”
Swansea have managed only one point since winning 2-1 at Aston Villa on October 24.
The Swans began the 2015/2016 campaign strongly, drawing 2-2 at Chelsea and beating United 2-1, but their form has since fallen away drastically.
“It was not a decision we took lightly, especially given Garry’s history and standing within the club,” Jenkins added.
“And it goes without saying that we wish Garry all the very best for the future and thank him for his tremendous service, not only as a player over the last decade, but also as our manager.
“He will always have a warm welcome at this football club. We hope to appoint a replacement as soon as possible.”
Brendan Rodgers and David Moyes who was recently sacked at Real Sociedad are potential successors to Monk.
