Cellulose nanocrystals (CNCs) based aerogels with extremely low density and hierarchical porous structure were constructed via a facile Pickering emulsion-templated strategy. In this method, aminated CNCs (CNC-NH2) were synthesized to stabilize o/w Pickering high internal phase emulsions (Pickering HIPEs). Amino groups were introduced to CNCs to decrease of net surface charges of CNCs, and enhanced their aggregation, and therefore to achieve Pickering HIPEs stabilized by the particles of ultra-low content (~0.1 wt%). A series of CNC aerogels was then obtained by freeze-drying these emulsions. The resulting aerogels were ultrahigh-light with a density that reached ca. 0.5 mg/cm3 (an order of magnitude lower than that previously reported for CNC aerogels), and an ultrahigh-porosity (up to 99.969%). Contributed to the extreme low density, the thermal conductivity of the aerogels was around 0.021 W/(m∙K) which is lower than that of air (0.024 W/(m∙K)). This novel strategy could be applied to other materials, such as graphene and carbon nanotubes, to prepare ultralight aerogels with controllable porous structures and unique properties.