When Tans joined Booking.com in 2002, the online travel site was a small start-up in Amsterdam. Today, she is CEO—she became boss in April 2016—and Booking.com, which generates the lion’s share of Priceline’s $10.7 billion in annual revenues, employs 15,000 people in 199 offices in 70 countries worldwide. Previously President and COO, Tans, in the past three years, has doubled the size of the organization as well as the number of accommodations on the platform to 1.3 million, more than any of its competitors. Tans is also making a push into China, which means forging a partnership with that country’s online travel leader Ctrip (led by No. 38 on this list).