This is a difficult question to answer definitively as there are a number of ways to measure "valuable." Some people might consider the most valuable startup to be the one that is currently worth the most money, while others might consider it to be the one with the most potential for future growth.
Some of the most valuable startups in the world include:
-Uber: Worth an estimated $68 billion as of August 2019, Uber is the world's most valuable startup. The company has experienced massive growth in recent years, and shows no signs of slowing down.
-Airbnb: Worth an estimated $31 billion as of August 2019, Airbnb is another rapidly-growing startup that is changing the way people travel. The company has disrupted the hotel industry and is now one of the most popular lodging options for travelers around the world.
-Pinterest: Worth an estimated $12.3 billion as of August 2019, Pinterest is a social media platform that allows users to share and discover new interests. The platform has a large and engaged user base, and is one of the fastest-growing social media sites.