Global warming is recognized as one of the most urgent challenges for human society in the 21st century. The international community has agreed to undertake necessary actions to prevent dangerous anthropogenic impacts on the climatic system. Based on the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (2014), the UNFCCC Parties adopted the Paris Agreement aimed at limiting the global mean surface temperature rise by “well below 2 degrees Celsius”. Such an ambitious “climatic” target requires unprecedented efforts to reduce carbon emissions to almost zero worldwide this century. Moreover, in order to keep the warming below 1.5°C, the global total emissions must be reduced by 50% or more by 2050 (compared to current levels) and reach net-zero levels afterwards. In practical terms, it means that most of the countries should deeply decarbonize their economies, energy systems, industries, transport, buildings, products and services, while continuing growth of GDP and the standard of living of the population. The developed countries agreed to take the lead in climate change mitigation under the UNFCCC; however, the largest developing countries and emerging economies have started playing substantial roles in carbon emissions nowadays. In this decade, China became the world No.1 CO2 emitter overcoming the United States. The Northeast Asian (NEA) region, including China, Japan, Mongolia, the Democratic People’s Republic of Korea, the Republic of Korea, and the Russian Federation, is responsible for annual emissions of over 12.4 billion tonnes of CO2 or approximately 40% of global energy-related CO2 emissions. These countries are huge contributors to global warming today and may increase their share further. The traditional way of combusting the huge fossil fuels reserves (coal, gas, and oil) available in the Northeast Asian region would emit greenhouse gases substantially exceeding the amounts that would warm the planet by 2°C. On the other hand, plentiful sources of renewable energy (solar, wind, hydro, tidal, and biomass, etc.) in combination with advanced technologies, investments, and land infrastructure developments can transform the Northeast Asian countries into decarbonized, climate- and environment-friendly economies with sustainable growth and development, fully consistent with the goals and commitments under the Paris Climate Agreement. Delays with the deep decarbonization of the Northeast Asian economies will impose higher risks for communities and life-supporting ecosystems, more losses and stranded assets for businesses, and slower technological progress worldwide. The analysis of challenges and opportunities in deep decarbonization pathways for the Northeast Asian region as a whole is presented in this publication. We raise many questions, and yet have not so many answers. By publishing this text, we want to invite all interested and concerned parties to start thinking about and debating these new, but very up-to-date issues of deep transformation of our economies, industries, consumer behavior, and ways of living in climate-neutral patterns, in order that we can urgently meet the need to save our planet and keep it in good shape for the generations to come.