Harrogate Road in Harewood has been shut after the HGV collided with the bike just after 10am today.
The air ambulance has landed and paramedics are at the scene treating the motorcyclist.
North Yorkshire Police have asked drivers to find alternative routes while emergency services work at the scene. The road is expected to be closed for several hours.
Anyone who witnessed the incident or the events surrounding it are asked to contact North Yorkshire Police on 101 quoting reference NYP-09082018-0617.