The 41-year-old actor said she believed ambitious women have the power to "change (the) society", reported FemaleFirst.
"A couple of years ago I wrote a speech of Glamour Women of the Year about why ambition in women is considered a dirty word. And we do kind of think, they've done all these studies at Harvard and Colombia about how women who have ambitious qualities are seen as selfish or self-serving, and it's actually completely the opposite.
"Usually they have a mission or a drive to help other people, or accomplish something. So I'm just trying to take the stigma off the word so we can encourage more little girls to be ambitious, because I do think that's how society will change," Witherspoon said on "Good Morning America".