Police said the ten-year-old was in a “stable” condition at the Victoria Hospital in Kirkcaldy in Fife. He has reportedly suffered head and back injuries.
The boy was in collision with a Stagecoach bus at around 5:30pm on Castle Road in Rosyth, close to the Rosyth Civil Sports Club.
No-one else was injured in the incident.
The road was closed at the scene yesterday, while police carried out their initial investigations.
Officers from Fife Constabulary are appealing for any witnesses to the incident to contact them.