An unidentified object went flying through an MTA bus driver’s window on the Upper West Side early Friday, police said.

The incident happened at about 7:14 a.m. on West 85th Street and Broadway when the M104 bus made a routine stop to unload passengers, according to the MTA.

That’s when the driver’s window suddenly shattered, cops said.

Police and the MTA say an unknown object struck the bus, but investigators still haven’t determined what the object was or where it came from.

Nobody on board was injured and the bus driver refused medical attention at the scene, authorities said.