Carbon dioxide (CO2) is regarded as a major contributor to global warming and the climate crisis. To mitigate its negative impacts, a potential strategy is adopted, namely converting CO2 into renewable fuels or valuable chemicals. Because of the sluggish thermodynamic and kinetic processes, catalysts (photocatalysts or electrocatalysts) are essential during CO2 reduction. In this review, fundamental concepts, catalytic principles and reaction pathways related to photocatalysis and electrocatalysis for CO2 reduction are provided, along with a survey of the progress in the rational design of new photocatalysts and electrocatalysts for CO2 reduction. Discussions in the field are mainly focused on the design strategies of catalysts that have been introduced to increase visible light excitation, improve charge separation and enhance CO2 adsorption of photocatalysts and alter electronic and geometric properties of electrocatalysts. Finally, recommendations and outlook for improving the selectivity of CO2 reduction and in achieving efficient, stable and selective CO2 photocatalysts or electrocatalysts are pointed out. © 2020 Society of Chemical Industry