The 70-year-old lasted just 13 matches since his appointment at the end of last season - he won only four of those games.
Two victories towards the tail end of the season saw Birmingham finish two points above the relegation zone and Redknapp was soon offered a one-year deal to stay on at St Andrews.
Redknapp spent around £20million on new recruits in the summer and broke the club's transfer record to buy Jota from Brentford for £6.5m.
But despite investing heavily in new players over the last few months, Birmingham have chose to axe the 70-year-old after six successive defeats, which sees them sitting second from bottom of the Championship.
Lee Carsley, Blues' head professional development coach, will step in as caretaker manager.
Vols Look For Another Breakthrough Against Florida
The last time they met, Tennessee ended an 11-game losing streak against the Gators with a 38-28 victory at Neyland Stadium. Florida has dominated Tennessee lately, taking 11 in a row in the series before the Volunteers won by 10 last season.
We thank him for all his efforts and wish him good luck for the future.
Harry Redknapp was sacked by second-tier Birmingham City on Saturday after his side lost a sixth successive match.
"It's not an excuse but today I had three of the forwards missing who I would have picked, probably the three most exciting players in all honesty".
The journeyman boss was brought in on short notice last season with just three games remaining.
Following a miserable opening to this campaign, they lie second from bottom of the table after losing six of their opening eight games.