In recent years, Unmanned Aerial Vehicles (UAVs) have proven to be invaluable in several industries that includes delivery, mining and surveillance etc. Protecting data integrity and achieving mission success depend on ensuring secure communication among UAVs and ground stations. To ensure the secure communication, a Chaotic Based Lightweight Authentication Protocol (ChLAP) is proposed. The proposed protocol uses the Kalpan-Yorke map to generate the encoded message. Considering the unique challenges of UAV networks, such as their finite resources and dynamic environments, this protocol prioritises rapid authentication and ensures robust data security. The proposed protocol combines adaptive security measures, a simplified authentication process, Physical Unclonable Function (PUF) and chaotic system that are optimised for resource efficiency to provide strong protection without sacrificing system performance. The simulation is done on Automated Validation of Internet Security Protocols and Applications (AVISPA) for validating the security of ChLAP. The experimental results show that it outperforms the other related protocol in terms of communication cost, computation cost and energy consumption. It is resistant to typical security risks such as message interception, manipulation, and illegal access.