Carousell
Founder Quek Siu Rui
Based in Singapore
Three years ago, Quek Siu Rui was offered US$100 million for his second-hand goods app—and said no. This was a shrewd move, as Carousell is now valued at about US$500m. If you’ve ever been to Marché aux Puces in Paris, then you’ll know how it works. It's a flea market that sells everything under the sun—tea cups, vintage jackets, silver spoons and record players—except it’s not under the sun, it’s on your phone. The 26-year-old founder focuses on Hong Kong, Singapore and Australia, but with a recent round of funding, the world is the limit.