Searching for new promising electrocatalysts with favorable architectures allowing abundant active sites and remarkable structure stability is an urgent task for the practical application of lithium-sulfur (Li−S) batteries. Herein, inspired by the structure of natural cactus, a new efficient and robust electrocatalyst with three-dimensional (3D) hierarchical cactus-like architecture constructed by functional zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) components is developed. The cactus-inspired catalyst (denoted as Co@NCNT/NCNS) consists of N-doped carbon nanosheets (NCNS) and standing N-doped carbon nanotubes (NCNT) forest with embedded Co nanoparticles on the top of NCNT, which was achieved by an in situ catalytic growth technique. The unique structure design integrates the advantages of 0D Co accelerating catalytic redox reactions, 1D NCNT providing a fast electron pathway, and 2D NCNS assuring strong structure stability. Especially, the rich Mott-Schottky heterointerfaces between metallic Co and semiconductive NCNT can further facilitate the electron transfer, thus improving the electrocatalyst activity. Consequently, a Li−S battery with the Co@NCNT/NCNS modified separator achieves ultralong cycle life over 4000 cycles at 2 C with ultralow capacity decay of 0.016% per cycle, much superior over that of recently reported batteries. This work provides a new strategy for developing ultra-stable catalysts towards long-life Li−S batteries.