In a statement, the internet search engine said that Ms Bartz was removed by the board of directors, effective immediately.
Her position has been filled by Tim Morse, Yahoo's chief financial officer, who will serve as interim chief executive while the board of directors will look for a new chief executive.
Yahoo faces increased competition from rivals such as Google and Facebook and Ms Bartz has struggled to change the company's fortunes, according to Larry Magid, a technology analyst at C-net.
He observed that Ms Bartz "hasn't done anything to change the company's fortunes, and they are still anxious to find a leader who can move them up".
"Facebook is way ahead, and now even Google is way ahead of Yahoo in social networking," he added.
