The project, known as stage four, will replace the Brownlow and Jennings stands, meaning new change rooms for the Geelong players, a new media centre and a rise in the stadium's capacity from 33,500 to 36,000.
At Tuesday morning's announcement, Cats chief executive Brian Cook thanked Labor leader Daniel Andrews for "such a generous offer".
"We deeply appreciate it," Cook added. "I think it's just an awesome, wonderful, courageous and probably very determined decision to make."
Geelong had seven home matches at Simonds Stadium this season, although the club is lobbying the AFL in an attempt to be granted eight home games at the venue next year.
But Cook is adamant that the stadium serves a much wider purpose than simply hosting football matches.
"We have 2000 or more events here every year," he said. "This is a community hub. This is owned by the community.
"Simonds Stadium will generate jobs, it will generate economic opportunity and will continue to make a sustainable community difference."
If Labor wins the election and stage four is completed, it will leave the Ford Stand and the Gary Ablett Terrace as the last areas to be redeveloped.
That project, which is known as stage five and will boost the stadium's capacity to 40,000, also has an approximate price tag of $70 million.
The Greater Geelong area contains a number of marginal electorates that will be crucial in deciding the Victorian election, which will be held on November 29.
