Abstract: The advent of the 5G era has stimulated the rapid development of high power electronics with dense integration. Three-dimensional (3D) thermally conductive networks, possessing high thermal and electrical conductivities and many different structures, are regarded as key materials to improve the performance of electronic devices. We provide a critical overview of carbon-based 3D thermally conductive networks, emphasizing their preparation-structure-property relationships and their applications in different scenarios. A detailed discussion of the microscopic principles of thermal conductivity is provided, which is crucial for increasing it. This is followed by an in-depth account of the construction of 3D networks using different carbon materials, such as graphene, carbon foam, and carbon nanotubes. Techniques for the assembly of two-dimensional graphene into 3D networks and their effects on thermal conductivity are emphasized. Finally, the existing challenges and future prospects for 3D carbon-based thermally conductive networks are discussed.