The actress and her husband Jim Toth welcomed their son Tennessee James today (September 27), People reports.
"Reese Witherspoon and husband Jim Toth welcomed Tennessee James into their family today," Witherspoon's spokesperson confirmed.
"Both mum and baby are healthy and the entire family is thrilled."
Witherspoon and Toth wed in March 2011, while reports emerged that they were expecting their first child together in March this year.
Witherspoon already has a 13-year-old daughter, Ava, and an 8-year-old son, Deacon, from her previous marriage to Ryan Philippe.