Researchers have synthesized a lanthanide–carbon triple bond encapsulated within an endohedral fullerene cage, specifically a cerium–carbide cluster [Ce≡CSc2] inside a C80 fullerene. This represents a pioneering stabilization of a lanthanide–carbon multiple bond, a rare and challenging chemical structure to isolate due to lanthanides’ typically weak bonding with carbon. Using X-ray crystallography, spectroscopic techniques, and quantum chemical calculations, the team characterized the extremely short Ce≡C bond length of around 1.97 Å. The fullerene cage plays a critical role in stabilizing this unusual trimetallic carbide cluster, protecting the reactive triple bond. This work provides new insights into metal–carbon bonding chemistry and opens avenues for designing lanthanide-based organometallic compounds with unique properties, with potential implications in catalysis and materials science.