The Real Madrid legend, 34, shared the news online, posting a picture with his new born and partner.
He wrote: “Immensely happy to be able to introduce Máximo Adriano.
“He was born at 6:56 p.m. and weighed 3.270kg. Mom and baby are perfect.”
Ramos and Pilar already have three boys, Sergio, five; Marco, four; and Alejandro, who will turn two in March.
They celebrity couple married in a star-studded ceremony last June at Seville Cathedral, having been together for seven years.
The footballer’s wife confirmed she was expecting in January on the Spanish TV show she stars in.
Her revelation, which was made live on prime time TV, followed speculation another child was on the way.
Model and TV celeb Pilar, who married Ramos last June in the southern Spanish city, confirmed her pregnancy after participating in a spectacular video which used her body to project graphics.
She made a name for herself as a reporter on a light entertainment show before starting to present some of Spain’s most famous television talent shows.
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In a magazine interview this year, she admitted: “If I got pregnant again, I wouldn’t mind if it was another boy.
“I know how they work. I think girls are more complex.
“But if it’s a girl, it would be great.” Ramos and Rubio have added to their young family Ramos and Rubio married in 2019 after seven years of dating