Tennessee James Toth was born Thursday, People.com said.
Where the baby was born and what he weighed were not immediately reported.
"Reese Witherspoon and husband Jim Toth welcomed Tennessee James into their family today," the Oscar winner's representative said. "Both mom and baby are healthy and the entire family is thrilled."
Little Tennessee is Witherspoon's first child with Toth, the talent agent she married in March 2011. She has a 13-year-old daughter, Ava, and 8-year-old son, Deacon, with her ex-husband, actor Ryan Phillippe.