The IAP2 Public Participation Spectrum is a foundational framework developed by the International Association for Public Participation that defines five levels of public engagement: inform, consult, involve, collaborate, and empower. Each level represents an increasing degree of public impact on decision-making processes, from one-way information sharing to full citizen control. This spectrum has become the gold standard for designing participatory processes in government, urban planning, and community development, helping organizations choose appropriate engagement methods based on their goals and constraints.