The ex-Bolton and Newcastle United boss was relieved of his duties along with his assistant Neil McDonald, and first-team coach Steve Kean will take temporary charge of the club.
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A statement on Blackburn's official website read: "The Venky's Group, owners of Blackburn Rovers Football Club, has today confirmed the departure of manager Sam Allardyce and assistant manager Neil McDonald with immediate effect.
"First-team coaching duties will be taken on by Steve Kean (currently first-team coach) for the immediate future.
"We have taken this decision as part of our wider plans and ambitions for the club.
"We would like to put on record our thanks to Mr Allardyce for his contribution to Blackburn Rovers Football Club."