Taylor Farrell, 27, met the victim, then 12, while working as a gymnastics coach in Melbourne, Australia.
He then began grooming her through Facebook, reports the Herald Sun.
The court then heard that he showered her with compliments before they proceeded to have sex and reportedly did so for several years.
This carried on "at least once a week" until the middle of 2014 at a range of locations include the "foam pit" at the gymnastics centre.
Judge O'Connell said: "The fact that the victim was so young, that is 12 years of age at the beginning of this offending, and the fact that the presumption of harm is not rebutted, means that general deterrence, just punishment and denunciation still have a role to play."
The victim felt "disgusted" each time they had sex.
She said: "I see now what Taylor did to me was wrong."
He later pleaded guilty at a committal hearing.
The twisted offender has been sentenced to three months behind bars and ordered to completed an 18-month community correction order.
Although the offending began in 2014, he was not arrested until 2018 following a complaint about his behaviour.
He was then charged in May last year.
He initially denied the charge and denied knowing her age, despite her age being listed on her Facebook Profile.
The judge considered his guilty plea, the delay since offending and a perceived low risk of re-offending.
However, he still decided he must serve jail time.
