The former Real Madrid, Manchester City and AC Milan player had been without a club since August when his deal with Turkish champions Basaksehir ended.
“This has always been my home,” Robinho said, after signing a five-month deal that takes him through to the end of the Brazilian league season. “My objective is to help on and off the pitch and get Santos in as high a place as possible.”
The 36-year old player won the Brazilian league, the Copa do Brasil and the Sao Paulo state championship with Santos in spells that began there in 2002.