The collision happened on the A658 at Leathley, near to the Riffa service station, at around 6.50am.
It involved a black pickup style vehicle, driven by a 58-year-old man from the Halifax area, and a black motorcycle.
The rider of the motorcycle - a 50-year-old man from the Harrogate area - suffered serious injuries and taken to Leeds General Infirmary.
A North Yorkshire Police spokesman said: "Officers are appealing for witnesses to the collision, anyone who recalls seeing the vehicles or anyone who recalls being overtaken by the motorcycle prior to the collision, to get in touch as soon as possible."
The road was closed for five hrs while emergency services attended to the casualty, to allow police officers to examine the scene and to allow the vehicles to be recovered.
Local diversions were put in place by highways.
Email [email protected] or call the force on 101, select option 2, and ask for Traffic Constable 117 Steve James to pass on information.
Please quote the North Yorkshire Police reference number NYP 12012018-0048.