#5 Marissa Mayer

On July 16, 2012, Mayer was appointed President and CEO of Yahoo!. She is also a member of the company's board of directors. In February 2013, Mayer oversaw a major personnel policy change at Yahoo! which required that all remote-working employees convert to in-office roles.

On May 20, 2013, Mayer led Yahoo to acquire Tumblr in a 1.1 billion dollar acquisition. In 2013, Mayer ranked 32 in the Forbes list of 100 most powerful women. She was the CEO of Yahoo! at age 37, making her the youngest CEO of a Fortune 500 company. The same day, she announced that she was pregnant — another first for the Fortune 500.

Previously, she was a long-time executive and key spokesperson for Google. Mayer joined Google in 1999 as employee number 20 and was the company's first female engineer. During her 13 years with the company, she was an engineer, designer, product manager and executive. She also oversaw the layout of Google's well-known, unadorned search homepage.

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