Harry Kewell and former Leeds United assistant manager sacked by Barnet
The former Whites player arrived at The Hive in June, having been sacked by Oldham Athletic last season following a seven-month stint as Latics boss.
Barnet were winless for all seven of Kewell's games as manager and a defeat by Bromley on Saturday left them 22nd in the 23-team National League.
Bees head of football, Dean Brennan, said: “It was clear how much Harry Kewell wanted to have a positive impact, but ultimately the results and the poor start to the season have dictated our decision.The plan for this season was for Barnet FC to be challenging in the top half of the table and that is still very much our aim."
Kewell's assistant Butler has also been sacked.
Butler joined Leeds United as assistant head coach during Thomas Christiansen's tenure as manager, leaving along with the Dane in February 2018.
He linked up with Kewell at Oldham Athletic early this year and remained at Boundary Park after the Australian's dismissal, before the pair teamed up again at Barnet in July.
Kewell, who previously took charge of Crawley and had a 14-game stint at Notts County, managed Leeds youngster Alfie McCalmont last season during the midfielder's loan spell at Oldham.