Complexity is not an anomaly. It is the substratum. Today, governments, global corporations, and multilateral bodies operate under technological acceleration, systemic pressure, permanent scrutiny, artificial intelligence, global interdependence, and existential risk. Yet the vast majority of institutions, organisations, and governance systems were designed for a world that no longer exists: stable, predictable, and linear. Architecting Human Systems reframes human systems not as structures to be managed, but as architectures to be designed. It is not a matter of administering inherited institutions, but of deliberately constructing them so that they may evolve without collapsing under conditions of high complexity. In this work, Fernando Privat develops a foundational framework —Human Systems Architecture (HSA)— that integrates strategy, governance, leadership, and institutional design into a single coherent system. The book introduces four original frameworks that enable the diagnosis, design, and evolution of human systems at any scale: from organisations to civilisations. Rather than focusing on management fashions or superficial technological solutions, Architecting Human Systems examines the layered architecture that underpins every institution: how purpose, strategy, and structure align; why some institutions endure for centuries whilst others collapse within decades; how institutional adaptability is designed; and what it means to govern evolutionarily rather than merely to operate. Grounded in systems thinking, institutional theory, complexity science, and real strategic experience with global leaders, the book proposes a new system operator: the Institutional Architect, a figure capable of designing human systems that are adaptive, legitimate, and evolutionary. What distinguishes this work is its capacity to connect systems thinking, institutional theory, strategy, and organisational design without lapsing into academic abstraction or managerial simplification. It elevates the author's work from leadership and strategy to the theory of human systems. In an era where artificial intelligence reconfigures power yet cannot assume institutional responsibility, the central challenge is no longer technology. It is the architecture of the systems that contain it. Civilisations do not collapse because their leaders fail in a crisis. They collapse because the design of their systems never permitted them to evolve.