The Greening the Blue Report 2021 provides a snapshot of the UN system’s environmental impacts throughout 2020 and its activities to reduce them. The 2021 edition of the Report covers data for 2020 on environmental impacts, including greenhouse gas emissions, waste, water, environmental management and, for the first time, procurement and human resources management functions. The Report includes data on 56 entities from across the UN system, representing approximately 315,000 personnel in Headquarters, in thousands of field offices and operations on the ground. It shows that in 2020, the UN system generated ~1.5 million tonnes CO2eq greenhouse gas (GHG) emissions, with per capita emissions of 5 tonnes CO2eq. In 2020, the emissions sources were 32 per cent from air travel, 12 per cent from other travel (rail, road, sea, etc.) and 55 per cent from facilities. In 2020, 19 per cent of UN electricity worldwide came from the use of renewable energies either purchased from the country grid or self-generated. The UN system was able to offset 99 per cent of GHG emissions. While offsetting is an important factor in managing unavoidable emissions, the priority for the UN system remains emissions reductions and elimination. This edition of the Report reveals the impacts of COVID-19 on the UN system’s environmental footprint. With significant worldwide travel restrictions and many UN personnel working from home, the UN system generated approximately 25 per cent fewer GHG emissions than in 2019. Several best practices show how these efforts are operated at ground level and what concrete results they have obtained.