Landmark birthday: Tasmanian man Roy Reeves celebrates 105 years

A man believed to be one of Tasmania's oldest citizens has celebrated his 105th birthday.

Roy Thomas Reeves has witnessed two world wars, 24 prime ministers and more than a century of Tasmanian history.

Mr Reeves has three children, 11 grandchildren, 23 great-grandchildren and two great-great-grandchildren.

Family members spanning five generations gathered in Hobart to help him mark the milestone.

Born just eight years after Federation, Mr Reeves has lived through all but three Australian prime ministers and received birthday wishes from the most recent three, as well as the regular Royal correspondence.

He has seen a lot of change in his long life.

"Air travel, cars, television - there's been huge change, hasn't there? Man on the moon," he said.

The secret to his longevity is good food, gardening and sport, with a few minor indulgences.

"I shouldn't say but he did smoke a pipe until he was 70, but he never really drank alcohol, a little shandy or something like that," said son Howard Reeves.

A keen Cats supporter, Mr Reeves has cheered Geelong on to nine premierships.

He is hoping this year they can make it 10 for him.