Information plays a central role in the organization and behavior of complex systems ranging from cells to societies, from neural networks to computational architectures, and from dissipative structures to adaptive agents. However, classical thermodynamics does not explicitly quantify the relationship between information and entropy in determining a system’s ability to organize, act, or evolve. I introduce here a new universal principle — the Principle of Informed Organizational Efficiency (IOE) — proposed as an Extended Fifth Law of Thermodynamics. This principle formalizes the competition between structured information and effective entropy using the ratio: R= I/S+1 where R denotes the system’s organizational efficiency, I the actionable information, and S its effective entropy. This relation quantifies how information promotes order while entropy promotes disorder, providing a fundamental organizational law applicable to physical, biological, computational, cognitive, and social systems. Through rigorous mathematical formalism, experimental predictions, and cross-disciplinary examples, I demonstrate that this law defines the organizational potential of any information-bearing system and complements — without contradicting — the four classical thermodynamic laws. It introduces a new, universal measure of system organization that offers predictive power over adaptation, learning, aging, collapse, and emergence.