Prince Albert II of Monaco has acknowledged that he has had an illegitimate child with a flight attendant from Togo, his lawyer said.
Prince Albert of Monaco has a reputation as a playboy prince
Lawyer Thierry Lacoste said in a statement that the prince, who is not married and has no heir, wanted to face up to his responsibilities.
He said the child, aged 22 months, would not be in line to the throne and would not have the name Grimaldi.
The prince, 47, said he hoped his son could avoid the media spotlight.
Prince Albert's father, Rainier III, died in April aged 81.
Rumours of the prince having a child with former Air France flight attendant Nicole Coste, who is Togolese and holds French citizenship, emerged in some parts of the French media days after Prince Rainier's death.
Ms Coste was quoted as saying she met the prince on a flight in 1997, leading to a relationship and the birth of the boy, Alexandre, in August 2003.
In the lawyer's statement, released as the Grimaldi family ends three months of mourning, the prince said he regretted the fact that the press had gone public with the story so close to his father's funeral.
"Prince Albert II asks the press to adopt responsible behaviour, similar to what it has adopted in similar circumstances for other public figures, and to respect his private life and that of the underage child," the statement added.
Prince Albert, often dubbed the "playboy prince", has for years appeared reluctant to get married or start a family, which perhaps prompted his father to change Monaco's constitution in 2002.
Previously, the principality would have become part of France in the absence of a male heir. Rainier had the law changed so that, in the event of Albert remaining childless, Princesses Caroline and Stephanie could follow their brother, who was proclaimed regent during Rainier's last days.
The sisters have seven children between them.
Mr Lacoste said the boy would have the same rights to inheritance as any other child of Prince Albert, should he have any others.