The presence of a head is a defining feature of bilaterian animals and a recurring design element in bioinspired robotics. While the structural forms differ considerably, the head serves analogous functions in animals and machines by concentrating sensory systems, neural processing, and motor control. This chapter examines the evolutionary origins and functional roles of the head, highlighting its contribution to voluntary movements, locomotor diversity, and adaptive behaviors. In bilaterians, cephalization has centralized sensory integration and motor coordination, enhancing survival through efficient predator–prey interactions, feeding strategies, and reproductive behaviors. The head position and mobility critically influence the biomechanical properties of locomotor patterns, across aquatic, terrestrial, and aerial environments. Sessile organisms also illustrate how sensory–motor integration contributes to survival strategies, emphasizing the broad ecological significance of head-related functions. By analyzing morphological designs, central pattern generators, and ecological constraints, we argue that the head represents an evolutionary innovation facilitating complex voluntary movements and behavioral plasticity. Comparative perspectives from robotics reveal that humanoid and animal-inspired machines often incorporate heads to improve navigation, interaction, and task performance. This chapter underscores the importance of integrating functional morphology, ethology, and biomimicry to better understand the role of the head in shaping performance and adaptability. Ultimately, this approach provides new insights to show how studies of biological functions can inspire the design of future autonomous robots and reversely.