EXCLUSIVE

G Herbo is now facing a battery charge for an altercation that went down with the mother of his child ... and prosecutors say the rapper dragged the woman by her hair.

TMZ broke the story ... G Herbo was arrested in Atlanta last month after cops said he assaulted Ariana Fletcher during an argument. According to new legal docs, obtained by TMZ, Herbo's been charged with one count of misdemeanor battery.

Prosecutors are accusing him of intentionally hurting Ari by dragging her by her hair and scratching her arm badly enough to leave visible wounds.

Prosecutors tell us the 23-year-old Chicago rapper -- who has a son with Ari -- is now staring down a possible max sentence of 1 year behind bars, if he's convicted.

As we reported ... Ari is now dating boxer Gervonta Davis, and she's pregnant with his child.