Synopsis Indian Ocean Atlas can be divided into three broad themes: physiographic characteristics and its bed, socio-historical, and economy, trade and natural resources of physical and economic importance. These themes are to meet the following objectives : (a) to reestablish India's intimate relationship with the ocean and the littoral countries, (b) to provide an assessment of the marine resources which would be required in near future, and (c) to provide a basis for economic and commercial cooperation among littoral countries which are mostly 'developing'. Historically, these countries were associated with India in some way or the other. These historical ties could be reestablished and strengthened. Keeping in view of the above-mentioned objectives, nineteen plates on different aspects have been prepared in such a manner that users would get a clear and informative maps. As the information relating to the preparation of thematic maps were available in different forms, considerable time had to be devoted in collecting and analysing the data and transforming them into a pre-decided map format. There is no atlas on Indian Ocean which serves the above purpose. National Atlas and Thematic Mapping Organisation, has, however, prepared maps on Indian Ocean and seas around the country. The map on 'Indian Ocean' (plate 93) of the National Atlas of India was, therefore, been used as the base map for this atlas. We have, however, consulted various institutions who have specialised knowledge on the different aspects of the Indian Ocean realm. Among them National Institute of Oceanography, Dona Paula (Goa), Department of Ocean Development (DOD), Indian Meteorological Department, Port Association of India, Geological Survey of India, Naval Hydrographic Office, Indian Institute of Port Management, Survey of India (Geodetic and Research Branch) and Fisheries Survey of India are worth mentioning. Further, published data were also collected from different publications of the United Nations and the World Bank.