Aerogels are highly porous structures produced by replacing the liquid solvent of a gel with air without causing the collapse of the solid network. Recently, 1D polymer nanofibers have been widely researched as building blocks to develop a new species of 3D fibrous aerogels with a physically entangled and/or chemically crosslinked fibrous network. 3D fibrous aerogels not only hold intrinsic aerogel properties such as an open-cell pore structure, low density, high specific surface area, and large porosity, but also benefit from the inherent features of polymer nanofibers including excellent mechanical flexibility and toughness, a wide range of material selection, and additional functionality. In this review, recent research progress in the fabrication and application of 3D fibrous aerogels is systematically summarized. Relevant strategies for constructing 3D fibrous aerogels, including electrospinning, solution blow spinning, freeze-drying, thermally induced self-agglomeration, and carbonization, are presented. Typical applications in energy (e.g., pressure sensors, triboelectric nanogenerators, electromagnetic interference shielding, etc.) and the environment (e.g., air filtration, thermal insulation, interfacial solar vapor generation, etc.) are highlighted. Finally, challenges in the fabrication of 3D fibrous aerogels, limitations for their use, and trends for future developments are discussed.