Sir Tim died early this morning, the Invercargill City Council said.
He served eight terms as Invercargill mayor and two terms as Waitematā mayor making him one of the longest-serving mayors in New Zealand.
His partner Asha Dutt described Sir Tim as "a kind-hearted man who cared deeply about the people around him".
“Today we lost the cornerstone of our family and the man who has devoted himself to promoting the city of Invercargill for almost 30 years.
"He was a champion for the underdog and an active political campaigner from his student days of anti-war protest, his activism for Māori rights, and his fight to keep the Southern Institute of Technology and Zero Fees autonomous.
"Tim will be remembered with gratitude, respect, and affection for his commitment to the south and his passion for life."
Invercargill Mayor Tom Campbell said Sir Tim's absence "will be deeply felt".
“Sir Tim served an incredible eight terms as mayor of Invercargill, and he leaves an enormous legacy within our community.
"He was widely known, not only for his genuine pride in our community and the people within it, but equally for his colourful personality, infectious enthusiasm, and his tireless advocacy for Invercargill – both locally and throughout the country."
When he was tapped for New Year Honours in 2018, Shadbolt told RNZ that being a good politician required people to "communicate in all ways".
"I like to think I am" a good politician, he said then.
"I guess it's the old cliché that the proof is in the pudding and we've had a golden run, really, in Invercargill.
"When I arrived there we were the fastest declining city in New Zealand or Australia, and we've turned that around, mainly with the zero fees schemes (at the Southern Institute of Technology) where we went from a thousand students to 5000 students, so it's good to actually be able to see changes that are significant."
He said the zero fees scheme changed Invercargill.
"Instead of being sort of a rural backwater, we were suddenly on the cutting edge of innovation and change and that to me is the project I feel most strongly about.
"The people of Invercargill are gritty, honest, hard working and prepared to take risks, and I was a risk."
An iconic personality
Shadbolt, with his trademark cheesy grin, became one of New Zealand's most readily identifiable personalities.
Born in Auckland in 1947, he attended Rutherford High and Auckland University.
He first came to national prominence in the 1960s as a student activist on issues like the Vietnam war and apartheid.
A talented public speaker and debater, he worked as a concrete contractor and was a member of the Auckland Regional Council.
In 1983, Shadbolt was elected mayor of Waitematā , and spent a colourful and at times controversial 6 years in the job.
In 1997, he sued Independent News for articles on the disappearance of the mayoral chain and robes 8 years earlier, and was awarded $50,000 in damages.
In 1992 he stood for mayor in Auckland, Waitakere and Dunedin, finishing third in each poll.
But the following year, Shadbolt was a mayor again, easily beating 13 rivals for the job in a byelection in Invercargill.
Voted out after only two years, he was re-elected in a landslide in 1998.
He lost his last bid for re-election in 2022.
He also showed an interest in national politics - he was the New Zealand First candidate for the Selwyn byelection in 1994, less than 24 hours after joining the party.
And in 1996, he was on the party list for the Aotearoa Legalise Cannabis Party.
Always prepared to make fun of himself, he appeared in a famous cheese ad featuring the line "I dont care where, as long as I'm Mayor".
Allied Media/RNZ
