The figure emerged in Facebook's first quarterly report to US financial regulators since the world's biggest social network made its much-criticised stock market debut in May.
The company said 8.7% of its 955m global users were not real.
There were 83.09m fake users in total, which Facebook classifies into three groups. The largest is made up of almost 46m duplicate profiles, accounting for 4.8% of all accounts. The company defined that category as "an account that a user maintains in addition to his or her principal account".
What were deemed "user-misclassified" profiles amounted to 2.4%, almost 23m, where Facebook says "users have created personal profiles for a business, organisation or non-human entity such as a pet".
Finally, "undesirable" profiles accounted for the remainder, about 14m, which are deemed to be in breach of Facebook's terms and conditions. The company said this typically means accounts that have been set up to send spam messages or content to other Facebook users.
In March, when Facebook last gave an estimate of the number of fake or duplicate accounts, it said the proportion was in the region of 5% or 6%, which at the time meant between 42m and 50m."