The Canaries confirmed Manning has been sacked after a 2-1 Championship defeat to Leicester City on Saturday at Carrow Road.
The 40-year-old Norwich-born, Bungay-bred coach departs after five months in charge at Carrow Road.
Manning presided over an unwanted club record eight consecutive home defeats and was the first City boss in 16 years to lose an East Anglian derby to Ipswich Town.
Long time assistant, Chris Hogg, plus first team coach analyst James Krause have also left the club.
Sporting director Ben Knapper told the club’s official site: “We have tried absolutely everything possible to work through this incredibly challenging period but, unfortunately, given the recent run of results and performances, we have been left with no choice other than to make a change at this stage.
“Liam and his staff worked tirelessly to move our football club forward. They are all fundamentally good people and we wish them the very best in whatever comes next.
“We very much understand the frustration and criticism from our supporters at this stage. So far, results and performances on the pitch haven’t been good enough.
“We accept that responsibility, but it’s now imperative that we start to repair the relationship with our supporters and do everything we can to give them something to get behind.”
The club statement also confirmed first-team coach, Ryan Garry, supported by keeper coach Tony Roberts and set piece coach Nick Stanley, will take charge of the first team on an interim basis, as the club works to appoint a new head coach.
Manning was Knapper’s number one choice to replace Danish boss, Johannes Hoff Thorup, in the summer after he was sacked 10 months into his Carrow Road tenure.
The former Bristol City boss did his post-match media following the latest Foxes’ loss but batted away questions on his own future.