The Urdaibai Biosphere Reserve Sustainable Development Strategy 2009-2015 represents the shared commitment of all public administrations in the Urdaibai region. It is an instrument that aims to coordinate all efforts to promote the region, fostering a balance between the conservation of natural resources and the achievement of sustainable economic and social development. Urdaibai is an area of unique value, a source of pride for the Basque Country, internationally recognized through its declaration as a Biosphere Reserve by UNESCO in 1984. The Basque Parliament approved Law 5/1989 on the Protection and Management of this area, with the aim of protecting and promoting the recovery of all its ecosystems, due to their natural, scientific, and environmental educational interest. The aim was to establish a model of territorial development that would allow the conservation of natural and cultural values without jeopardizing its economic and social development. The Urdaibai Sustainable Development Strategy 2009-2015 aims to take advantage of all the synergies generated in the Basque Country with the implementation of numerous sectoral and cross-cutting plans (Biodiversity Strategy 2008-2014, Basque Plan to Combat Climate Change 2008-2012, Basque Plan for Environmentally Sustainable Consumption 2006-2010, Basque Country Energy Strategy 3E-2010, among others) to advance towards the fulfillment of the objectives set out in the Basque Environmental Strategy for Sustainable Development. Furthermore, this document represents the culmination of a long participatory process that has brought together institutional, social, economic, and territorial actors, both private and public, as well as the general public, with the aim of using this Strategy to guide the future and make Urdaibai and, by extension, the Basque Country a benchmark as an innovative territory for research, experimentation, and the development of initiatives aimed at achieving a balance between the conservation of natural heritage and economic and social development.