Ann Cairns started her career in the North Sea, designing and testing pipelines for oil rigs. She was the first female engineer to work on offshore oil rigs in the UK—an environment that she’s said was less sexist than her next workplace in the investment banking industry. She worked for decades in banking—including 15 years in senior operational roles at Citigroup and overseeing the European side of Lehman Brothers Holdings International’s bankruptcy—before becoming #2 at MasterCard in 2011, overseeing all international growth. She is responsible for operations in all countries outside of the United States—generating 61% of the global payments technology company’s total net revenue of $9.5 billion last year. —Claire Groden