The video, which was shared on Facebook, shows the teenager dragging another girl around by her hair and punching and kicking her as children watch.
It is understood the incident happened in the Cowdenbeath area of Fife, Scotland, on Sunday.
The cameraphone footage shows the bully drag the girl to her feet by her hair before she knees her in the face.
It also shows the bully swinging a punch at her victim as surrounding children shout “fight, fight, fight”.
The victim is then pushed to the floor by her attacker who bangs the girl’s head on the road several times.
Police confirmed they had investigated the video and that a 15-year-old girl had been charged in relation to the incident.
A Police Scotland spokeswoman said: “Police in Fife have charged a 15-year-old girl in connection with an assault in the Cowdenbeath area.
“The incident was reported to police on Sunday, August 16.
“A report will be submitted to the Children’s Reporter.”