The Sahara and Sahel Observatory (OSS) is an international, intergovernmental, award-winning organization established in 1992 and based in Tunis (Tunisia) since 2000. OSS holds the King Hassan II World Water Prize (2012 edition) and is an Accredited Implementing entity for the Adaptation Fund. OSS operates as a platform for North-South-South partnerships on the environment and sustainable development, The organization works in Africa’s Sahel-Sahara region, which comprises 26 member countries located in North Africa (the Arab Maghreb Union – UMA – zone and Egypt), West Africa (the Permanent Interstates Committee for Drought Control in the Sahel – CILSS – zone) and East Africa (the Intergovernmental Authority for Development – IGAD – zone). OSS members also include 7 non-African countries, 5 sub-regional organizations, 8 international organizations and a non-governmental organization. OSS aims to support regional member countries’ policies and action in the field of sustainable natural resource management with a view to enabling sustainable development. Environmental monitoring and the joint management of transboundary aquifers, in particular, constitute two fields where OSS has gained international recognition. Over the last two decades, the organization’s operational scope has gradually evolved to encompass several themes that include but are not limited to: • IWRM, hydrological modelling and the study of linkages between aquifers and surface water • Study of the socio-economic and agricultural aspects pertaining to water use (irrigation) • Support to the implementation of the MEAs on desertification, climate change and biodiversity • Drought Early Warning • Climate change adaptation • Green Economy • Long-term environmental monitoring • Communication for Development