The Young Adult actress's spokesperson confirmed that she is the "proud mum of a healthy baby boy named Jackson".
In 2010, the actress ended her relationship with Night Stalker star Stuart Townsend after a holiday trip to Mexico.
The pair met while filming Trapped in 2001 and dated for nine years prior to the split.
Theron, who has been romantically linked to Keanu Reeves andRyan Reynolds, previously confessed that she has always been in relationships ever since her teenage years.
"I've never been single. This is the first time in my life," she shared. "From the time I was 19, I've been in relationships, literally gone from one to the other within a month."
Theron can be seen next in Ridley Scott's Prometheus, which opens to theatres on June 1 in the UK and June 8 in the US.
Watch the teaser trailer for Prometheus below: