Ribosome hibernation preserves translation machinery during stress, yet its mechanisms in Archaea remain poorly defined. Here we identify Hib, a previously unrecognized family of archaeal hibernation factors. Genetic, structural and biochemical analyses show that Hib binds ribosomal subunits, blocking the mRNA channel and tRNA sites to inactivate translation. Deletion of hib in Thermococcus barophilus delays recovery from stationary phase and reduces 70S ribosome pools, establishing its role in ribosome preservation. Hib displays a unique modular architecture, combining a bacterial-like HPF module with tandem CBS domains. Cryo-EM structures reveal conformational heterogeneity of Hib:ribosome complexes, consistent with dynamic engagement, and the CBS-containing N-terminal domain binds adenine nucleotides, suggesting a link between hibernation and energy status. These findings define Hib as a key archaeal hibernation factor and provide a framework for understanding ribosome dormancy and adaptation across all domains of life. ### Competing Interest Statement The authors have declared no competing interest. Agence Nationale de la Recherche, https://ror.org/00rbzpz17, ANR-25-CE12-4161

Funded #M2 #Internship (6 months) — Montpellier | IGMM × ISEM We are recruiting a motivated M2 student to join a joint project on Hox factors beyond DNA, testing how RNA binding by conserved transcri...