Pc Rebecca Barnett was dismissed from Thames Valley Police following a disciplinary hearing which found that her off-duty actions amounted to gross misconduct.
Pc Barnett has previously pleaded guilty to a charge of GBH without intent in relation to the incident which happened on June 10 2017, in Banbury, Oxfordshire.
She will be sentenced at Oxford Crown Court on June 11.
A force spokesman said: "Whilst off duty, Pc Barnett became involved in an argument with a woman, and a scuffle ensued.
"Pc Barnett then grabbed the woman and bit her on the nose, causing a significant injury, which required surgery and has left the victim with permanent scarring."
Deputy Chief Constable John Campbell said: "Pc Barnett's actions were very much below the standards expected of an off-duty police officer.
"Barnett has been convicted of a violent offence and it would be completely unacceptable for her to continue in her duties protecting the public as a serving police officer."