The Industrial Internet Reference Architecture (IIRA) is a comprehensive framework that serves as a foundational blueprint for developing industrial internet systems. Formulated to address the unique requirements and challenges of integrating digital technologies with physical processes in an industrial context, IIRA outlines key architectural patterns, design principles, and standards to guide the development of robust, secure, and scalable solutions. Created by the Industrial Internet Consortium (now part of the Object Management Group), the IIRA aims to accelerate the adoption of the Industrial Internet of Things (IIoT) by providing a common language and set of best practices that can be customized to suit specific industrial sectors. By doing so, it helps organizations make informed decisions when designing and implementing IIoT systems, thus facilitating interoperability, reducing risks, and improving efficiency.