Fox gave birth to the baby boy named Journey River Green on August 4, 2016, reported E! online.
The 30-year-old "Teenage Mutant Ninja Turtles" star and Green, are also parents to three-year-old son Noah and two-year-old son Bodhi.
The actress confirmed her pregnancy in April at Cinema Con, when she stepped out sporting a visible baby bump.
Though Fox filed for divorce from Green, whom she has been with for more than 10 years, in August 2015, sources close to the couple insist they have called off their split.
They've also been spotted out together many times since, from celebrating Fox's 30th birthday to romantic dinner dates, to lunch outings with their two older sons.
