Multiple sources have reportedly confirmed the news to this tabloid, with one insider saying Reese is "12 weeks along." It will be the first baby for Witherspoon and husband Jim Toth, who got married in March 2011.
The star has two children - Ava, 12, and Deacon, 8 - with ex Ryan Phillippe.
"The timing is right," says an Us Weekly source, adding that Witherspoon only plans on telling a small circle of loved ones for now. "She's so happy!"
And we're so happy for her! Congrats to the couple and best wishes to the new family!