7 pages, 4 figures, 2 tables.-- The data that support the findings of this study are available from the corresponding author upon reasonable request Trophic studies are key to understand the ecological role of marine species in natural ecosystems. In this study, we examined the trophic ecology of the holocephalan rabbitfish Chimaera monstrosa, a demersal chondrichthyan considered Near Threatened by the Mediterranean red list assessment of the IUCN. The study was based on the analysis of the stomach content of 86 individuals inhabiting deep-sea waters of the Gulf of Lions (northwestern Mediterranean Sea). Additionally, to the description of the diet and trophic position of this species, we compared its diet between sexes and maturity stages. The results revealed that the rabbitfish in this Mediterranean ecosystem is a mesopredator, specialized on the consumption of crustaceans and feeding almost exclusively on the decapod Monodaeus couchii, independently of sex or maturity stage. These results grant new information about the trophic ecology of this rarely studied species in the Mediterranean Sea JN was funded by the Spanish National Program Ramón y Cajal (RYC-2015-17809). This study is a contribution to the projects RESNEP (CTM2017-82991-C2-1-R, Ministry of Science and Innovation, Spain) and ECOTRANS (CTM2011-26333, Ministry of Economy and Competitiveness, Spain). This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation(CEX2019-000928-S) Peer reviewed