This special issue seeks to bring together contributions of a nascent community of scholars studying infrastructure delivery models; what they are, how they are created, and how they change over time and across institutional fields. This area of research is crucial to advancing the field of project management and, with its links to neighboring fields such as innovation, organizational theory, and strategic management, is a fertile ground for developing new insights and knowledge. Before we introduce the articles that make up the special issue, we describe the policy environment and drivers for innovation in infrastructure delivery models, situate infrastructure delivery models within project management scholarship, and provide some conceptual scaffolding for considering the nature of innovation in delivery models. We then turn to a discussion of how each article in the special issue advances our knowledge of delivery models and project management. Drawing inspiration from the articles, we conclude by sketching out the building blocks and core conceptual components of a delivery model, and laying the foundations for a more nuanced comparison of existing, emerging, and novel delivery models over time and across institutional fields. What is Infrastructure and Why Is It Important? Infrastructure incorporates the systems, network utilities, constructs, and other physical assets that underpin and enable social and economic development (Bell, 1973; Chandler, 1977). It connects firms and markets and provides people, communities, and organizations with essential services. It creates significant benefits, both directly through the services it delivers, and indirectly, through the impact of those services on the rest of the economy. Countries depend on infrastructure to move people, materials, goods, and information rapidly, efficiently, and reliably between geographical locations (e.g., road, rail, aviation, and telecommunications); to provide access to dependable and secure sources of water and energy (e.g., water, gas, electricity, nuclear, and renewables); to process and treat waste (e.g., sewer systems and incineration plants); to educate, support, and protect a literate, healthy, and law-abiding population (e.g., schools, public housing, prisons, and hospitals); and to create a culturally diverse and advanced civil society (e.g., sport stadiums, opera houses, and other distinctive buildings). Infrastructure is expensive to build, operate, and maintain, and often produces large negative externalities, such as CO 2 emissions, noise, and pollution. It is typically long-lived, so the costs of any poor choices, let alone mistakes, can last for generations. And, as we will see, major infrastructure projects are often delivered late, over budget, and fail to achieve their expected benefits. Given its importance for the prosperity of societies in the 21st century, public and private actors are searching for new and improved ways of delivering infrastructure projects. In mature market economies, governments in the United Stat...