Rigid polyurethane foams (RPUFs) represent a versatile class of closed-cell polymers known for their outstanding mechanical strength, thermal insulation, and wide-ranging applications. Unlike flexible foams, RPUFs are structurally rigid, using a cellular matrix that traps gases to minimize thermal conductivity. These characteristics make RPUFs indispensable in industries requiring energy-efficient insulation and structural durability, including construction, automotive, and aerospace sectors. RPUFs are primarily synthesized through a reaction between polyols and isocyanates, allowing for customizable properties through various chemical compositions and production techniques. The use of bio-based polyols, derived from renewable resources, is emerging as a promising innovation for reducing environmental impact while preserving foam performance. Advances in computational modeling, such as thermodynamic, kinetic, and mechanical simulations, have significantly refined the development process, enabling precise predictions of RPUF properties and behavior under different environmental conditions. This chapter provides an overview of RPUFs, covering their history, synthesis methods, applications, and the latest advancements in sustainable materials and computational modeling techniques, positioning RPUFs as a crucial material in modern engineering and green technology.