He was born on Tuesday 19 June at a hospital in Los Angeles, weighing 6 lbs and 13 oz.
The couple told the publication: “We are so grateful for this beautiful blessing.”
The magazine published the first image of Longoria with her new son.
In the image, the new mother appears to cradle her newborn as he rests his head on her chest wearing his hospital beanie.
Throughout her pregnancy, the Overboard actress documented her progress on social media.
Ahead of the birth, Longoria told how she walked every day to get her son “here faster.”
She said: “Thank God there’s a human coming out of this experience.”
Longoria added that she felt “uncomfortable” during the last weeks of her pregnancy.
The birth of Santiago comes two years after Longoria and Bastón married in a lavish ceremony in Mexico.
Longoria is suspected to raise her son with husband Bastón in a mansion located in Bel Air Crest.