S tewart Butterfield is a Canadian technology entrepreneur who has the rare distinction of co-founding two iconic and transformative internet companies: Flickr and Slack. His first major success was Flickr, a pioneering photo-sharing website that he co-founded in 2004. Flickr was one of the earliest and most influential Web 2.0 applications, popularizing online photo sharing and social tagging. It was acquired by Yahoo in 2005.

His second, and much larger, success came from an unexpected pivot. He and his team were developing a web-based multiplayer game, but the game ultimately failed. However, the internal communication tool they had built for themselves to collaborate on the project proved to be incredibly effective. They decided to commercialize this tool, which became Slack. The workplace collaboration and messaging platform was launched in 2013 and became a massive global success, transforming how teams communicate. Slack went public via a direct listing in 2019, and in 2021, it was acquired by Salesforce for $27.7 billion, a deal that cemented Butterfield's billionaire status. He left Slack and Salesforce in 2022.