The Paris Agreement signalled global consensus to keep average temperature rise “well below” 2 °C by the end of the century. Results from integrated assessment models have made it increasingly evident that negative emissions (removing CO₂ from the atmosphere) are crucial to achieving this. Consequently, negative emissions technologies (NETs) have come to the forefront of mitigation discussions. NETs must however overcome challenges if they are to be realised at scale. Uncertainties around the large-scale biomass supply have fuelled a debate on whether negative emissions from bio-energy with carbon capture and storage (BECCS) are sustainably achievable, if at all. Reliable carbon accounting frameworks and policy incentives are needed to improve investment prospects. The direct extraction of CO₂ from air, or direct air capture (DAC), has since been demonstrated as a source of negative emissions. The large energy and economic costs associated with extracting CO₂ from air are proving prohibitive to achieving commercial viability of DAC technology. Without dedicated policy support for technological innovation, and further interdisciplinary research to constrain a variety of uncertainties, the world risks foregoing a portfolio of technologies that add much-needed flexibility in the mitigation toolbox. This chapter details the evidence for negative emissions, proposed means of achieving them and their barriers to commercial effectiveness.