Brazil World Cup winner Ronaldo is in intensive care in Ibiza suffering from pneumonia.
The 41-year-old former striker tweeted that he was taken ill on Friday but hopes to be discharged on Monday.
Ronaldo scored 62 times for Brazil, including both goals when they beat Germany in the 2002 World Cup final.
The former Real Madrid forward, who also played for Barcelona, Inter Milan and AC Milan, thanked his fans for their love and well wishes.
A spokesperson for Can Misses Hospital, where Ronaldo is being treated, said she was unable to give any information for privacy reasons.
Ronaldo was on holiday in Ibiza, where he owns a home.
The striker's career ended seven years ago when he hung up his boots up after two years with Corinthians in Brazil.
Ronaldo won two La Liga titles with Real and the Uefa Cup with Inter. He was part of the Brazil squad who won the 1994 World Cup – although he did not play – and helped them reach the 1998 final.
He picked up the Ballon d'Or award for the best player in the world in 1997 and 2002.