A 38-year-old biker from Merseyside died in the first crash on the A65 near Ingleton at 2.45pm.
Less than three hours later a 61-year-old rider from Leeds was fatally injured in a second accident, again on the A65, just south of Settle.
Three cars were involved in the first collision - a red VW, a black Audi S3 and a blue Saab 93, and a blue Yamaha YZF—R1 motorcycle.
The VW driver, an 83-year-old woman from Keighley, was arrested following the accident. She has been released under investigation while enquiries continue.
The second involved a silver Citroen Berlingo and a blue Suzuki GSX 1250 motorcycle.
The 61-year-old rider was taken to Leeds General Infirmary by air ambulance but sadly died a short time later.
The 45-year-old Citreon driver from Leeds was uninjured.
Families tributes to friends who died in East Yorkshire aircraft crashSergeant Hamish Halloway from the Major Collision Investigation Team said; “Both of these devastating incidents happened on the A65 in the Craven area within a few hours of each other.
"I am appealing to anyone who was travelling on the A65 yesterday to get in touch with North Yorkshire Police. Even if you did not witness the collisions, you might have some information which could assist the investigations into these tragic events.
“Please call 101 with any information, quoting the reference numbers. If you are out of the North Yorkshire Area then please dial 101, press the hash key and say “North Yorkshire Police”.
“My thoughts remain with all those involved in the collisions, especially with those who have lost a loved one”.