Industrial-scale ammonia synthesis, as accomplished by the Haber–Bosch process, was a landmark achievement of the 20th century. However, as currently practiced, including feedstock generation, the process accounts for 1–2% of global energy demand and contributes significant fossil-fuel-based CO2 emissions. Accordingly, there is much contemporary interest in developing more sustainable ammonia synthesis routes which could, for example, be operated on the local scale employing renewable energy. The five themes of this Faraday Discussion unite different research communities around a topic of mutual interest and great societal importance, with particular emphasis placed upon the transfer of learning between the different themes. The discussion focuses on the following themes:Heterogeneous catalytic and chemical looping routes to N2 activationElectrocatalytic and photocatalytic routes to N2 activationEnzymatic N2 activationHomogeneous N2 activationAlternative routes to NH3 and its applications