Reese Witherspoon post baby body dress sunglasses barneys baby

Someone dropped the baby weight in record time!

Just THREE weeks after giving birth to her third child, Reese Witherspoon went shopping at Barneys in Beverly Hills on Tuesday afternoon, and she gave us a peek at her slimmed down post-baby body.

Tennessee's mama kept it simple with a black dress, shades and a red tote, and we haven't seen her newborn son just yet, but we have a feeling we'll get to very shortly! Wonder if he looks more like Reese or hubby Jim Toth?