The Harold Mitchell Foundation, founded in 2000, confirmed his death on Saturday in a message on its website.

“He was a wonderful man who helped so many. He will be sadly missed,” it read.

Mr Mitchell was recuperating from knee replacement surgery when he died.

He founded Mitchell & Partners in Melbourne in 1976 and grew it into Australia’s largest media buying agency before selling to British company Aegis in 2010.

Mr Mitchell was made a companion of the Order of Australia for his leadership and philanthropy in the arts, health, education and humanitarian support for Timor-Leste and Indigenous communities that same year.

He was a national finalist for Australian of the Year in 2013.

Government Services Minister Bill Shorten was shocked to hear of his friend’s death and said it was a privilege to have known him.

“There can only ever be one Harold Mitchell,” Mr Shorten wrote on social media platform X, formerly Twitter, remembering Mr Mitchell as “an avuncular renaissance man who was energetically interested in everything and everyone”.

Victoria University, where Mr Mitchell’s eponymous policy research thinktank the Mitchell Institute is based, remembered him as a generous and transformational donor.

“His legacy will live on,” Victoria University vice-chancellor Adam Shoemaker said in a statement on Sunday.

“We will continue to drive educational transformation on a national and international stage to honour his memory,” he said.