McConaughey and Alves began dating in 2006
US actor Matthew McConaughey and his Brazilian girlfriend Camilla Alves are said to be "tired and elated" following the birth of their baby son.
"We are so happy to have created the greatest miracle in the world - having a child and making a family," the Fool's Gold star told OK magazine.
"Now comes the greatest adventure - raising one, together."
Levi Alves McConaughey was born Monday night in California, according to the actor's publicist.
The baby, who weighed 7 pounds and 4 ounces, is the couple's first.
"We welcome Levi into this wonderful life and look forward to livin' it in the mean time and all times," McConaughey wrote on his official website.
The actor said he and Alves had been "side by side" throughout the birth.
The 38-year-old, whose films include A Time to Kill and The Wedding Planner, said Levi was another name for the biblical apostle Matthew.
McConaughey will shortly be seen in action comedy Tropic Thunder alongside Ben Stiller, Jack Black and Robert Downey Jr.