Officers are investigating the crash and are appealing for witnesses and anyone with dashcam to come forward.
At 4.10pm today a five-vehicle collision occurred on the A35 at Winterborne Abbas involving a grey Triumph motorcycle, a black Aprilia motorcycle, a bronze Nissan pick-up, a silver Kia Sportage and a grey Volkswagen Transporter.
The rider of the Triumph – a man aged in his 50s and from Marlborough – was airlifted to Southampton General Hospital with life-threatening injuries.
The rider of the Aprilia – a man aged in his 50s and from Bristol – sustained potentially life-changing injuries and has was airlifted to Southmead Hospital in Bristol.
One other person sustained minor injuries.
The A35 is closed between Bridport and Dorchester and the closures are expected to remain in place for several hours while collision investigators examine the scene and officers speak with witnesses.
Police Sergeant Lee Savage, of the traffic unit, said: “An investigation into this collision is now underway and I am would ask anyone who witnessed the incident, and has not yet spoken to officers, to please contact me.
“I am particularly keen to hear from anyone who witnessed the two motorcycles being ridden eastbound along the A35 from Bridport to Winterborne Abbas prior to the collision, and especially anyone who captured either vehicle on dashcam.
“The road remains closed to allow for our examinations to be carried out and I would like to thank members of the public for their patience and understanding.”
Anyone with information is asked to contact Dorset Police at www.dorset.police.uk, via email email@example.com or by calling 101, quoting occurrence number 55210063724. Alternatively, to stay 100 per cent anonymous, contact the independent charity Crimestoppers online at Crimestoppers-uk.org or call Freephone 0800 555 111.