Gary Rowett has left Burton to become Birmingham's new manager.
Burton have announced the 40-year-old has been appointed as the replacement for the sacked Lee Clark at the Blues and will take his backroom staff of Kevin Summerfield, Kevin Poole and Mark Sale with him to St Andrew's.
He joins a side reeling from Saturday's 8-0 home hammering by Bournemouth which left them second bottom in the Sky Bet Championship.
Rowett was the club's first choice while Owen Coyle and Mike Phelan were also reportedly in the frame.
The 40-year-old returns to Birmingham 14 years after he was sold to Leicester for £3million following a successful two-year spell as a player. He made 106 appearances for the club between 1998 and 2000 before finishing his playing career at Burton in 2007 after a spell at Charlton.
Rowett won 63 of his 142 games at the Brewers after he replaced Paul Peschisolido in March 2012 and lost 1-0 to Fleetwood in the Sky Bet League Two play-off final last season. He had guided them to third in the table this term and lost his final game in charge 1-0 at Stevenage on Saturday.
Rowett's first match at Birmingham will be Saturday's Midlands derby with Wolves at St Andrew's.
Burton, meanwhile, have put head of academy Mike Whitlow in caretaker charge, assisted by senior players Ian Sharps and Lee Bell.
Brewers chairman Ben Robinson told the club's official website: "After the success Gary has achieved at Burton Albion over the last three years it was inevitable that there would be interest from other clubs.
"Gary is an ambitious young manager and the offer from one of his former clubs playing Championship football was one he wanted to take. We wish him well and thank Gary and his coaching team for what they have done for the club."