Large volume shrinkage and high temperature are frequently encountered problems during the preparation of graphene aerogels via hydrothermal reactions. Here we report the dopamine-mediated fabrication of ultralight graphene aerogels (UGAs) with low volume shrinkage via hydrothermal reactions at low temperature. The UGAs were fabricated by the hydrothermal reaction of the graphene oxide (GO)/dopamine colloidal solutions at 85 degrees C in the presence of dopamine followed by freeze-drying and pyrolysis. The interaction between GO and dopamine in the aqueous phase, the effects of various parameters on the formation of the UGAs, the roles of dopamine in hydrothermal reactions as well as the wettability and electrical conductivity of the UGAs were investigated using a wide range of analytical techniques. The GO concentration, dopamine concentration, and the temperature and time of the hydrothermal reaction have great influences on the formation of the UGAs. The addition of dopamine forms crosslinking points among the GO sheets and results in the partial reduction of GO in the hydrothermal reaction. In addition, the N atoms of dopamine were doped into the graphene sheets. The UGAs feature low volume shrinkage (8.3%), ultralow density (3.5 mg cm^-3), excellent superhydrophobicity/superoleophilicity (CA(water) similar to 155.5 degrees and CA(oil) similar to 0 degrees), very high absorbency for organic liquids (134.0-282.9 g g^-1) as well as excellent fire retardant properties and high conductivity (3.07 S cm^-1). All these merits make the UGAs very promising materials for absorption of organic pollutants, sensors, energy storage, etc.