This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book begins with challenges certain matters which are often taken for granted in the literature and the practice of regional planning and regional governance. It addresses what may broadly be called 'institutional' matters, the frameworks within which regional planning is taking place. The book examines the overall development of regional planning historically, places this within the context of recent spatial policy making in the European Union, and also describes current developments in Wales. It explores the frontier of the new themes that might be addressed by Regional Planning Guidance (RPG), or related regional policy documents, in the future. The book also addresses the potential contribution of the regionalisation policies to environmental sustainability. It looks at the scope for sustainable or 'balanced' development through regional planning.