This paper addresses the development and validation of free-space path loss models for reconfigurable intelligent surface (RIS)-assisted wireless communications. RISs, which consist of tunable unit cells, have gained significant attention due to their ability to manipulate electromagnetic waves, offering potential improvements in performance and coverage with cost-effective and energy-efficient solutions. The authors develop three free-space path loss models for different scenarios, considering factors such as the distance from the transmitter/receiver to the RIS, the size of the RIS, near-field/far-field effects, and antenna radiation patterns. These models are validated through extensive simulations and experimental measurements conducted in a microwave anechoic chamber using fabricated RISs. The experimental results align well with the modeling outcomes, confirming the accuracy of the proposed models. The study highlights the importance of considering physical factors in RIS-assisted wireless communications and provides a foundation for further theoretical and practical advancements in this field.This paper addresses the development and validation of free-space path loss models for reconfigurable intelligent surface (RIS)-assisted wireless communications. RISs, which consist of tunable unit cells, have gained significant attention due to their ability to manipulate electromagnetic waves, offering potential improvements in performance and coverage with cost-effective and energy-efficient solutions. The authors develop three free-space path loss models for different scenarios, considering factors such as the distance from the transmitter/receiver to the RIS, the size of the RIS, near-field/far-field effects, and antenna radiation patterns. These models are validated through extensive simulations and experimental measurements conducted in a microwave anechoic chamber using fabricated RISs. The experimental results align well with the modeling outcomes, confirming the accuracy of the proposed models. The study highlights the importance of considering physical factors in RIS-assisted wireless communications and provides a foundation for further theoretical and practical advancements in this field.