The 33-year-old joined Arsenal on a free transfer after seven seasons with Chelsea but struggled as he scored just once in 37 matches for the north London side across all competitions.
- Don't have ESPN? Get instant access
The Brazil international's father recently explained it was his son's desire to join the Sao Paulo side, when he told Arena SBT: "There are things money can't buy. Playing for Corinthians is priceless.
"Today, it is possible to pay [Willian's salary] -- without doubt. Especially as Corinthians are lowering their balance sheet. Two three players there that are leaving would allow them to pay [it].
"Playing for Corinthians is priceless, but he is professional. If it depended on him, he would go to Corinthians."
Willian made his debut for Corinthians in 2006 before he left to join Shakhtar Donetsk after two seasons.
Willian was also part of the Brazil side which won the Copa America on home soil in 2019.