<p>The healthcare industry has undergone a significant transformation with the advent of the Internet of Medical Things (IoMT), enabling remote diagnosis, monitoring, and treatment of patients without requiring the physical presence of physicians. However, using open wireless communication channels to transmit sensitive information introduces vulnerabilities to privacy and security breaches. Entity authentication is critical to safeguarding IoMT systems, as its compromise can lead to severe consequences. To address these challenges, this research proposes a lightweight and robust certificate-less signature-based mutual authentication scheme for IoMT systems. The proposed scheme employs certificate-less cryptography to eliminate certificate management overhead and integrates advanced cryptographic constructs, including elliptic curve cryptography (ECC) and a one-way generic hash function, while avoiding computationally expensive bilinear pairing and map-to-point operations. This ensures secure and efficient communication. Formal security analysis using mathematical proof techniques evaluates the scheme's resistance to attacks, while informal testing is conducted under various attack scenarios. Comparative performance analysis reveals that the proposed system reduces communication overhead by 252 bytes and computation time by 0.89 s, significantly enhancing system efficiency. These findings demonstrate the scheme's effectiveness in improving operational performance and ensuring reliable communication in IoMT systems.</p>