Bryan Johnson (born August 22, 1977) is an American entrepreneur, venture capitalist, writer and author. He is the founder and CEO of Kernel, a company that can monitor and record brain activity, and OS Fund, a venture capital firm that invests in early-stage science and technology companies. He was also founder, chairman and CEO of Braintree, a company which specializes in mobile and web payment systems for ecommerce companies. Braintree acquired Venmo in 2012 for $26.2 million; the combined entity was acquired by PayPal in 2013 for $800 million.