The 54-year-old, who takes over with immediate effect, will be presented at a press conference at Ewood Park at 4pm on Thursday.
Blackburn moved quickly after sacking Paul Ince on Tuesday and have swooped for the former Bolton and Newcastle boss.
The club said in a statement: "Blackburn Rovers are delighted to announce the appointment of Sam Allardyce as manager with immediate effect. Sam has signed a three-year contract."
Rovers were keen to make an appointment as soon as possible - especially as Allardyce had also been linked with the vacant position at Sunderland.
Blackburn chairman John Williams had said it would be a huge advantage for the new manager to be in position before the Premier League visit of Tony Pulis' Potters.
Williams said: "You can't underestimate how much of a boost a physical presence could have on Saturday for what is an absolutely mammoth game.
"Everyone needs to know how big this game is as this is a time the club really has to come together."
Allardyce's eight successful years as Bolton boss persuaded the Rovers board that he is the man to rescue Blackburn from the threat of relegation.
Blackburn are currently second from bottom of the Premier League with 13 points from 17 games.
TEAMtalk Football News | Latest News |
Blackburn moved quickly after sacking Paul Ince on Tuesday and have swooped for the former Bolton and Newcastle boss.
The club said in a statement: "Blackburn Rovers are delighted to announce the appointment of Sam Allardyce as manager with immediate effect. Sam has signed a three-year contract."
Rovers were keen to make an appointment as soon as possible - especially as Allardyce had also been linked with the vacant position at Sunderland.
Blackburn chairman John Williams had said it would be a huge advantage for the new manager to be in position before the Premier League visit of Tony Pulis' Potters.
Williams said: "You can't underestimate how much of a boost a physical presence could have on Saturday for what is an absolutely mammoth game.
"Everyone needs to know how big this game is as this is a time the club really has to come together."
Allardyce's eight successful years as Bolton boss persuaded the Rovers board that he is the man to rescue Blackburn from the threat of relegation.
Blackburn are currently second from bottom of the Premier League with 13 points from 17 games.
TEAMtalk Football News | Latest News |