This paper introduces The Playing Zone, a unified framework identifying a recurring three-zone regulatory architecture across six distinct domains of human experience: nervous system regulation, interpersonal behaviour, physical and developmental practice, attentional function, social proximity, and capacity development. In each domain, two dysregulated extremes bracket a functional middle ground, here termed The Playing Zone or the Adaptive Range, where genuine response, growth, choice, and engagement become possible. The six constituent frameworks are the Window of Tolerance (Siegel, 1999), the Assertive Range, the Discomfort Zone, the Attention Scale, the Proximity Range, and the Capacity Range. Each is described, their shared architecture identified, and their practical implications for regulatory development examined. The convergence of this pattern across independent domains is proposed as a candidate organizing principle of human regulatory function, generating testable hypotheses for cross-domain research. Implications for practice in counselling, somatic education, martial arts, mental health services, and organizational development are discussed. This paper sits within a broader research programme examining self-regulation across scales, alongside The Regulatory Singularity (2025) at civilizational scale and The Capacity Era (2026) at institutional scale. Version note: This version adds a standard title page and citation block, corrects the reference list by removing two uncited sources and adding two instruments cited in the text, and removes trademark notation throughout. Version 2.1 of April 2026 preceded these changes.