B rian Acton is an American computer programmer and internet entrepreneur who co-founded the instant messaging application WhatsApp with Jan Koum. An early employee at Yahoo, where he worked for over a decade, Acton famously applied for jobs at both Twitter and Facebook and was rejected. Undeterred, he teamed up with his former Yahoo colleague, Jan Koum, to create a new kind of messaging service that was simple, ad-free, and respected user privacy.

WhatsApp launched in 2009 and grew virally to become the world's most popular messaging app, with hundreds of millions of users. The company's massive success culminated in 2014 when Facebook acquired WhatsApp for a staggering $19 billion in cash and stock, making Acton a multi-billionaire overnight. He remained at Facebook for a few years before leaving over disagreements about the future monetization of the app and the use of user data. A staunch advocate for privacy, he has since used his fortune to co-found the Signal Foundation, which develops the encrypted messaging app Signal and champions secure communication.