The footballer’s girlfriend, 28, made the announcement alongside three adorable photos of the child sleeping peacefully in her cot.
The baby was born on April 18, but the child’s twin brother tragically died at birth.
She wrote in her caption: ‘Bella Esmeralda [green heart] 180422.’
The Manchester United striker and the former sales assistant revealed that their son had died at birth on April 18, but their daughter survived.
An emotional statement announcing the news said: “It is with our deepest sadness we have to announce that our baby boy has passed away. It is the greatest pain that any parents can feel.
“Only the birth of our baby girl gives us the strength to live this moment with some hope and happiness.
“We would like to thank the doctors and nurses for all their expert care and support.
“We are all devastated at this loss and we kindly ask for privacy at this very difficult time. Our baby boy, you are our angel. We will always love you.”
Ronaldo is already father to Cristiano Jr, 11, and twins Eva and Mateo, 5. Bella is Ronaldo and Georgina’s second child together, after the Argentinian model gave birth to Alana Martina, 4, in November 2017.