APIs have become vital to the digital economy, enabling seamless integration and communication between different systems and services. The API Platform Engineering Maturity Model serves as a framework for organizations to assess and enhance their API capabilities, guiding them through various maturity stages, from basic ad-hoc management to a differentiated, sophisticated platform. This model emphasizes the strategic orchestration of technology, governance, and people to drive innovation, efficiency, and growth. It outlines the progression through stages—Basic, Foundational, Intermediate, Advanced, and Differentiated—each characterized by specific technological, procedural, and personnel developments. As organizations advance, they integrate best practices in APIOps, enhance documentation and discovery processes, and ensure robust governance and security, supported by specialized roles and collaborative efforts. The model advocates for aligning API strategies with business goals, fostering a culture of continuous improvement and collaboration, and utilizing governance institutions like the API Community of Practice to facilitate this journey. Ultimately, this maturity model provides a strategic roadmap for building a scalable, trustworthy, and adaptable API ecosystem that supports digital transformation and business growth.