The child was hit just after 3:30 p.m. Friday at an intersection in northwestern Las Vegas.
Police say the bus was making a right turn and for unknown reasons she fell under the bus. She died at the scene.
School officials say three children were on the vehicle.
Police are asking parents who were picking up their children at the time of the accident to contact police with any information.
Meanwhile, another child was struck while on a sidewalk a few miles away after a driver lost control of their vehicle late Friday.
That child was taken to a local hospital with non-life threatening injuries.
Neither child was immediately identified.