Dallas Archer, 19, was being searched when a female prison officer detected an "unknown item in her crotch", according to a police report.
The teenager from Tennessee was found to be hiding a stolen 22-calibre pistol - which was four inches in length - in her vagina.
The police report reads: "[We] recovered a North American Arms 22 LR revolver (loaded) which Ms. Dallas had concealed in her vagina.
"The pistol was recovered and checked through the NCIC and was stolen from an auto burglary in 2013."
The gun was stolen from a car last year and its original owner, 70-year-old John Souther, has since told The Smoking Gun he would like the "little fellow returned".
However he added the weapon would require "a bath in bleach".
The teen was charged with possession of a firearm and introducing contraband into a penal facility.
She has since been released on bail.