A 60-year-old man from Florida has been taken to hospital in Newcastle with "serious injuries", after his bike collided with a car on the A66.
The accident happened at Threlkeld, near Keswick.
The driver of the car was uninjured in the accident.
Motorists are asked to follow the diversions in place.
More top news
A shoplifting pensioner who threatened supermarket staff with a knife as he tried to flee has been sent to prison
According to Cumbria Police, motorcyclists have the highest rate of collisions and casualties per mile travelled
Three brothers from Cumbria have become the first people to swim across the two biggest and most powerful whirlpools in the world.