Scotland Yard said that a misconduct hearing on Friday found that the actions of 48-year-old Couzens breached the standards of professional behaviour in respect of discreditable conduct.
The hearing, chaired by Assistant Commissioner Helen Ball, dismissed Couzens without notice, the force added.
Ms Ball said: "Couzens has betrayed everything we, the police, stand for and following his guilty pleas and convictions I have dismissed him today.
"All of us in the Met are horrified, sickened and angered by this man's crimes.
"Sarah was a young woman who had her life cruelly snatched away from her. I know she is sorely missed by so many people and our thoughts remain with her loved ones.
"We are so profoundly sorry."
The force said it held an accelerated hearing as quickly as possible following Couzens' guilty plea and conviction on July 9.
Couzens could spend the rest of his life behind bars for the kidnap, rape and murder of Ms Everard, who he snatched as she walked home alone from a friend's house in Clapham, south London, on the evening of March 3.
The sexual predator, who had clocked off from a 12-hour shift that morning, went on to rape and strangle the 33-year-old marketing executive.
Scotland Yard had launched an urgent inquiry after Ms Everard was reported missing by her boyfriend, Josh Lowth, on March 4.
Couzens, a firearms-trained parliamentary and diplomatic protection officer, wiped his phone just minutes before he was arrested at his home in Deal, Kent, on March 9.
The following day, a week after she disappeared, Ms Everard's body was found in a woodland stream in Ashford, Kent, just metres from land owned by Couzens.
The killing has sparked protests at the rate of violence against women.
On July 9, Couzens pleaded guilty to Ms Everard's murder, having previously admitted her kidnap and rape.
During the 20-minute hearing, Lord Justice Fulford discussed the possibility of a whole-life order as he adjourned sentencing until September 29.
The police watchdog has received a string of referrals relating to the Couzens case, with 12 officers being investigated.
The Independent Office for Police Conduct (IOPC) is investigating whether the Met failed to investigate two allegations of indecent exposure relating to Couzens in February, just days before the killing.
Kent Police are also being investigated over their response to a third allegation of indecent exposure in 2015.
The Met said that Ms Ball, following consultation with interested parties including the Crown Prosecution Service, had decided the misconduct hearing should be heard in private.
Although normally public, the force said the need for transparency in misconduct proceedings was "significantly outweighed" by the risk of interfering with criminal proceedings.
Having considered the representations put forward, Ms Ball decided that there remained a "real risk" of undermining the criminal case despite Couzens' guilty pleas, it added.