Willian, a former winger for Chelsea and Arsenal, left Corinthians after allegedly receiving death threats on social media for himself and his family.
Since returning to Corinthians from Arsenal in the summer of last year, the 34-year-old has scored only once in 45 appearances.
The international from Brazil has previously been connected to a Fulham comeback to the Premier League.
“Willian asked us for his [contract] termination,” said Corinthians president Duilio Monteiro Alves.
“We are sad not to have him any more and also because it didn’t go the way we expected. But we have to keep those here that are happy.”
Willian played in the second leg of Corinthians’ quarterfinal Copa Libertadores match against regional rivals Flamengo on Wednesday. Corinthians, who have dropped five of their last nine games, were eliminated by Flamengo.
“Whenever Corinthians lost and I didn’t play well, my family received threats and insults on social media – my wife, my children, and recently they also started attacking my father, my sister,” Willian told the Globo Esporte website.