Monk, one of the youngest managers in the league at 36, had been with the club for over 11 years, first as a defender and then manager since February 2014, when he replaced Michael Laudrup. Saturday’s 3-0 home defeat by Leicester City was his last game in charge, and left them 15th in the table.
“The decision has been made very reluctantly and with a heavy heart,” chairman Huw Jenkins said. “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. “We hope to appoint a replacement as soon as possible.”
Assistant manager Pep Clotet and first-team coach James Beattie are also set to leave.
Alan Curtis, the former Swansea player and long-time coach at the club, is expected to be in charge of the team for Saturday’s Premier League match at Manchester City.
Monk had guided the Swans to a highest ever Premier League finish of eighth in his first full season. They started this season in similar form, drawing at champions Chelsea on the opening day before beating Newcastle United and Manchester United at home in an unbeaten four-match start. But Swansea’s form then deteriorated as they lost four of their next six games.
An away victory over Aston Villa at the end of October interrupted the winless run, but the pressure intensified on Monk as his team picked up only one point in their next five games.
Former boss Brendan Rodgers is the favourite to succeed Monk. Rodgers left the Liberty Stadium for Liverpool in June 2012, and is currently out of a job having been replaced at Anfield by Jürgen Klopp in October. Former Everton and Manchester United boss David Moyes is also in the running.