Digital platforms are transforming industries, yet research has predominantly focused on start-ups or pure platform firms, overlooking the unique challenges and opportunities faced by incumbents transitioning to platform business models. Existing studies in this domain are fragmented, often limited to single firms, industries, or organizational aspects. To address this gap, we analyze 88 incumbent-owned platforms across multiple industries and integrate them with prior conceptual work. We develop a taxonomy of incumbent-owned platform business models comprising 10 dimensions and 26 characteristics and empirically derive six archetypal business models from this taxonomy: C2C Platforms, Community Platforms, Product Ecosystems, Hybrid Service Platforms, Data Ecosystems, and Independent Platforms. Beyond classification, we formulate propositions on transformation pathways incumbents follow, strategies they apply to overcome the chicken-and-egg problem, and business model factors shaping platform success, survival, and failure. Our study contributes a comprehensive, empirically grounded framework that advances theory on platform business models and offers managers a structured tool to navigate strategic options and anticipate challenges in platform transformation.