The incident happened just before 9.30pm last night (April 19) as the motorcycle headed towards the A61 from Swindon Lane and the lorry headed towards Leeds.
North Yorkshire Police said that the 47-year-old driver of the lorry, who is also from Leeds, did not suffer any injuries but was left shocked by the incident.
A spokesperson for NYP said: "The rider, a 21-year-old man from Leeds, suffered serious head and chest injuries.
"He was taken by ambulance to Leeds General Infirmary where he is receiving treatment."
The road was closed until 4.10am today (April 20).
Motorists were warned to avoid the area by Harrogate officers on Twitter.
The lorry driver is now assisting officers with their investigation but police have appealed for witnesses to help establish the circumstances.
A spokesperson for NYP said: "Witnesses to the collision or anyone who recalls seeing either the blue and white motorcycle or the white HGV prior to the incident, are urged to call North Yorkshire Police on 101, select option 2, and ask for Hamish Halloway.
Alternatively email [email protected] Please quote reference number 12180067106."