Ruth Porat

In a surprise hire, Google tapped the former Morgan Stanley CFO as its finance chief in May. Just three months later, Porat gained even more clout when Google created a holding company, Alphabet, to oversee Google and its other businesses—and named her CFO of that company too. She’s off to a good start: After presenting second-quarter 2015 earnings, Google’s market cap rose by $65 billion.

For more on newcomers and returns to the list, read “Who's on? Who's off? Fortune's list of the Most Powerful Women has plenty of changes.”