The collision happened at around 5.50am today on Aberdeen's King's Gate, near the junction with Forest Road.
The 29-year-old rider of the Honda bike was taken to Aberdeen Royal Infirmary, where he died a short time later from his injuries.
Police Scotland said the road was closed to allow investigations to take place at the scene.
Anyone who witnessed the collision or may have seen the motorcycle in the area is asked to contact police on 101.
Elsewhere, around half an hour later, there was a fatal road traffic collision on the A9.
The one-vehicle crash happened about three miles south of Dalwhinnie at around 6.20am.
It is understood one vehicle occupant was killed in the crash.
The A9 at Dalwhinnie was closed to traffic in both directions following the incident. Motorists have been asked to avoid the area as the road is expected to remain closed for some time.
Police later confirmed a man who was driving the car had died. He was the only person in the car.