Almost two-thirds of humanity live around the Indian Ocean, many in countries dependent on fisheries and rain-fed agriculture that are vulnerable to climate variability and extremes. Coastal population growth is conflating with climate change to increase vulnerability. The Indian Ocean alone has absorbed 60% of the global oceanic heat uptake over the last decade and the fate of this heat and its impact on future change is unknown. The Indian Ocean observing system (IndOOS), established in 2006, is a multinational network of sustained oceanic measurements that underpin understanding and forecasting of weather and climate for the Indian Ocean region and beyond. Yet gaps in the IndOOS have so far limited forecasting efforts, left large discrepancies in the basin energy budget, and kept us in the dark about ecosystem stressors. A three-year, international review of the IndOOS by more than 60 scientific experts highlights the need for an enhanced observing network that can meet regional scientific and societal challenges. Here we present core findings from the review, including the need for 1) chemical, biological, and ecosystem measurements alongside physical parameters; 2) expansion into the Arabian Sea; 3) better resolved upper-ocean processes to yield improved understanding of air-sea coupling and rainfall forecasts; and 4) expansion into key coastal regions and the deep ocean to better constrain the basin-wide energy budget. These goals will require new partnerships, creating opportunities for Indian Ocean rim countries to enhance their monitoring and forecasting capacity.