Allardyce has signed a three-year-contract with Rovers.
An announcement on their official website said: “Blackburn Rovers are delighted to announce the appointment of Sam Allardyce as manager with immediate effect.
“Sam has signed a three-year-contract.
“A Press Conference will be held at Ewood Park at 4.00pm tomorrow (Thursday).”
Allardyce will replace Paul Ince who was sacked from the job earlier this week.
