Dropbox is a file hosting service operated by the American company Dropbox, Inc., headquartered in San Francisco, California, that offers cloud storage, file synchronization, personal cloud, and client software. Dropbox was founded in 2007 by MIT students Drew Houston and Arash Ferdowsi as a startup company, with initial funding from seed accelerator Y Combinator.

Dropbox has been ranked as one of the most valuable startups in the US and the world, with a valuation of over US$10 billion, and it has been described as one of Y Combinator's most successful investments to date. However, Dropbox has also experienced criticism and generated controversy for issues including security breaches and privacy concerns.

Dropbox has been blocked in China since 2014. It received a five star rating in the Electronic Frontier Foundation's 2017 "Protecting Your Data From Government Requests" report.