The industry platform is a distinct organizational form that has grown in importance over the past 20 years. We focus on the digital platform, which, along with its associated ecosystem, is uniquely positioned to create and capture value in the digital economy. We clarify the key mechanisms by which platform organizations create and capture value. One type of digital platform, which we call innovation platforms, enables third-party firms such as software developers to build hundreds or even millions of applications that enhance the functionality of foundational products like Microsoft Windows or Google’s Android. The other type, which we call transaction platforms, includes companies such as Uber, Airbnb, Facebook, Alibaba or Amazon’s marketplace. These organizations link buyers and sellers and thereby reduce search and transaction costs for millions and billions of consumers and providers. Both types of platforms involve unique organizational forms that extend beyond traditional firm boundaries and supply chains governed by contracts to broader, less formal, and usually global “ecosystems” of innovators and suppliers of various products and services in the digital economy. This chapter suggests a framework that describes the principal strategic choices managers and entrepreneurs need to make if they want to build a successful platform business. It also outlines the social and regulatory challenges associated with the rising dominance of the most powerful platform companies.