This paper provides an account of the development of the web-based Okavango Collections (OC) metadata catalogue. In light of climate change, growing population, and developmental pressures on the transboundary Cubango Okavango river basin, there is an urgent need to ensure timely access to reliable environmental data and information for environmental decision-making. Commissioned by the Permanent Okavango River Basin Water Commission (OKACOM), OC provides a searchable directory of collections of data, data sets, image archives, books, reports and other information available both in the region and in other parts of the world. It is based on GeoNetwork Opensource, a standards-based and open source web catalogue, implementing international standards for metadata content and system interoperability. Its main features include a geospatial catalogue application, providing metadata editing and advanced search and discovery capabilities, and an integrated map viewer. Key development challenges included the creation of a regional geographic names thesaurus as a controlled vocabulary for place keywords, an email notification system to facilitate ongoing maintenance of metadata records, improved contacts management, and enhanced search and discovery functionality. In addition to providing an important environmental information service for the Cubango Okavango region, and a key tool to facilitate negotiation of river basin data sharing among the riparian states, OC potentially offers a model system for implementation elsewhere. Keywords: transboundary river basin, Cubango-Okavango river basin, information systems, metadata, spatial data infrastructure.