Italian media reacted enthusiastically to the €117 million deal, with the daily Corriere della Sera calling it "a dream come true", but not everyone was pleased with the news. The USB trade union called the acquisition unfair, announcing a strike spanning three days.
Both Juventus and Fiat Chrysler Automobiles, which has a large plant in Melfi, are part controlled by holding company Exor.
"It is unacceptable that while the workers of FCA and [Exor-owned vehicle manufacturers] CNH Industrial have been continually asked for huge economic sacrifices for years, the same company decides to spend hundreds of millions of euros on purchasing a footballer," USB said.
It went on to say that the companies' employees had been subjected to "a life of misery" and "unequal treatment, [which] cannot and should not be accepted", calling on the owners to invest in new car models to guarantee the future security of Fiat workers and to improve the finances of "thousands of people instead of just one".
In a second statement, USB said they were "baffled" by the response to the strike, which they described as a "fuss".
The strike is set to take place at FCA between 10pm on Sunday and 6am on Tuesday.
Consumer rights organization Codacons also criticized the Ronaldo transfer, calling it an "immoral and shameful contract" and pointing to the growing number of ordinary Italians living in poverty, as highlighted recently by both the Bank of Italy and statistics agency Istat.
Ronaldo's transfer to Juventus was announced by his current club Real Madrid on Tuesday. The Turin side claimed a seventh straight Serie A title last season, but thanks to a Ronaldo penalty was beaten by Real Madrid in Europe.