The man and woman from Launceston were riding south near Lilydale in the state's north at about 3pm on Sunday when police say they passed a white Western Star truck towing a trailer, laden with round bales of hay.
"The hay bale was still moving when it struck the motorcycle, having fallen from the truck," police said in a statement.
Both victims died at the scene and investigations into the crash are continuing.
The first in Tasmania's string of fatalities occurred late on Saturday night when a Mazda ute crashed off a corner while driving on King Island.
A man behind the wheel, the ute's sole occupant, was rushed to hospital but died a short time later.
At 11am (AEDT) Sunday police were alerted to a single motorcycle crash near Bothwell in central Tasmania.
The 57-year-old man riding the bike died at the scene.
Police have also reported a two-car smash on Tasmania's major Midlands Highway near central Tunbridge about 4pm (AEDT) which led to one occupant being airlifted to hospital in a critical condition.
© AAP 2015