This book introduces platform firms as unique business models. Leveraging on the early literature on network economics and strategy frameworks, this book explores how platform business firms evolve in the modern business world. Taking a strategic perspective, this book engages the reader with core concepts, case studies, and frameworks for analyzing platform business firms. This book differentiates platform business firms from traditional pipeline firms; explores engagement with different actors, value creation, and operations of platforms; elucidates resources and capabilities of platform firms that provide them sustained competitive advantage; analyzes performance levers in operating platform business models, including complementarities with other business models; and discusses the sustainability of platform business models, in the face of regulatory and societal challenges, among others. The book is designed as a primer for entrepreneurs setting up and operating platform business firms, senior managers in large corporations repurposing their resources to initiate network dynamics in their businesses, early career managers, and professionals engaging with myriad platform firms for their professional and personal needs. This book intends to provide a decision-maker with a portfolio of decisions to make to create, operate, sustain, and generate value out of a platform business firm. It is also useful for policy professionals to appreciate the economics and policy implications of regulating and governing platforms in a post-digital world.