The petrochemical industry has a substantial impact on the environment through the use of large quantities of natural resources (mass and energy) and discharge of wastes into the environment. Process integration offers a powerful framework for the sustainable development of the petrochemical through conservation of mass and energy and synergism among the different building blocks in the supply chain. The chapter provides an overview of process integration basics and tools that can be used to enhance the performance of the petrochemical industry. The chapter also describes the key building blocks of the petrochemical supply chain and how they may be integrated. Finally, the chapter describes key drivers and opportunities of process integration within individual petrochemical plants, among various petrochemical facilities, and the relationship to the existing refining infrastructure.