A poignant message on the All Blacks website, beneath a photograph of Hobbs celebrating a Rugby World Cup win with captain Richie McCaw, said: "We've lost a very dear friend, a rugby great and an incredible New Zealander."
NZRU chairman Mike Eagle said it was "with a heavy heart that we acknowledge the passing of an incredible New Zealander".
"New Zealand has lost an inspirational leader with an incredible passion for the game of rugby and the part it plays in our lives.
"I know many New Zealanders will join us in expressing their sorrow at his passing."
NZRU chief executive Steve Tew added: "Rugby has lost a great friend. We will all miss his integrity, dogged determination and incredible sense of justice."
Helen Clark, who as Prime Minister led the charge with Hobbs to win the World Cup rights, said on Twitter that he was an "outstanding New Zealander, instrumental in bringing RWC2011 to New Zealand".
Colin Meads said Hobbs was "the man who saved New Zealand rugby".
"New Zealand has lost its greatest administrator. If he hadn't been in ill health Jock would now be the chairman of the IRB. His legacy is [bringing] rugby back to New Zealanders as our great game. Many more are followers of the game because of his efforts.
"I'll always remember Jock as a great friend. He was always Jock. And when he relaxed he could enjoy himself in a big way. We got on well together. It's a very sad day."
Prime Minister John Key said he was incredibly sad at the news.
"I have known Jock for a long time and have enjoyed his company on many an occasion. We have talked and laughed and discussed the country's political and sporting problems. I will miss him very much," he said.
"Jock was the man who convinced Dublin that New Zealand should host last year's Rugby World Cup. This was possibly his finest hour. Winning the trophy was certainly one of New Zealand's finest hours.
"I know I join with Jock's wife Nicky, his four children, and many friends in being very grateful for the time we had with him. I join with all of them in celebrating his life and knowing that ours will be the poorer without him."
Sport and Recreation Minister Murray McCully also described Hobbs as one of nature's gentlemen and an outstanding sportsman.
"It is literally correct to say that had it not been for the roles that Jock played at a critical time, professional rugby would not be the sport it is today."
IRB chairman Bernard Lapasset said Hobbs' contribution to rugby was "exceptional", and extended his condolences to his family and friends on behalf of the IRB.
"Among numerous highlights, he provided the vision, passion and leadership that secured New Zealand the right to host RWC 2011 and as chairman of RNZ 2011 those qualities laid the foundations for a hugely successful tournament of which New Zealanders and the global Rugby family can be proud."
Chris Moller was the chief executive of the NZRU during Hobbs' tenure as chairman.
The pair worked closely together and Moller was devastated by Hobbs' death.
"It's terribly sad for him, for his family and for rugby in this country frankly," he said.
"He was a great statesman of New Zealand rugby. He was an All Black captain, which there aren't many of."
He said Hobbs stepped in when the union was in crisis after losing the sub-hosting rights to the 2003 Rugby World Cup, and then had the chore of securing last year's tournament for New Zealand.
"I am so delighted that Jock was here for the whole of that."
Former All Blacks Craig Innes, Filo Tiatia and Pita Alatini, via Twitter, spoke of their sadness at Hobbs' death.
All Blacks Jerome Kaino, Liam Messam, Zac Guildford and Corey Jane also posted condolences.
The Wallabies paid tribute, saying: "On behalf of Australian Rugby, we send our condolences to the family of Jock Hobbs following his passing this afternoon."
