The previous Tottenham and Portsmouth boss then signed a 1-year offer May to remain on as Blues boss.
Former Blues midfielder Lee Carsley continues to be placed temporarily in control.
Speaking following the loss to Preston before his departure was announced, Redknapp told BBC WM 95.6: “Fans deserve better which was my motivation to keep this year.
The 70-year-old required control of the club with three games remaining last term, winning the ultimate two games to prevent relegation around the final day.
Redknapp had replaced Zola 16 hrs following the Italian’s resignation in April, following a Blues’ dismal run of two wins in 24 matches underneath the former Chelsea forward.
Redknapp initially labored without requesting payment from Blues for that final three games of 2016-17, getting replaced Gianfranco Zola.
Birmingham signed 14 players throughout the summer time transfer window, but six defeats using their first eight league games of 2017-18 saw Redknapp end up being the first managing casualty from the Championship season.
“We thank him for those his efforts and need him best of luck for future years. There won’t be any further comment at the moment.Inch
Birmingham City have separated company with manager Harry Redknapp following six straight defeats in most competitions.