The Puerto Rican singer, known as the King of Latin Pop, captioned the post: “Nuestro hijo Renn Martin-Yosef ha nacido,”
It translates as “our son Renn Martin-Yosef was born”.
Martin, 47, and Yosef, a 35-year-old artist, married in 2017.
They are also parents to 11-year-old twins Matteo and Valentino and daughter Lucia Martin-Yosef, who was born late last year.
Martin announced he and Yosef were expecting a fourth child at an event in Washington DC in September.
“I love big families,” he said.
Martin has sold more than 70 million records around the world, making him one of the most successful Latin artists ever.
He is also a successful actor and earned an Emmy Award nomination for his supporting role in 2018 drama The Assassination of Gianni Versace: American Crime Story.
Ricky Martin welcomes fourth child with husband Jwan Yosef