A novel moderately thermophilic and halophilic bacterium, designated strain M0105^T, was isolated from mangrove sediment collected in the Beibu Gulf, south China. The isolate is Gram-negative, non-motile and rod-shaped bacterium with smooth colonies of pale-yellow appearance. Growth occurs at 15–46 °C (optimum 37–40 °C) and pH range of 6.0–10.0 (optimum pH 8.0–9.0). It required 1–7% NaCl (optimum 3–5%) for growth. Strain M0105^T was affiliated to the family ‘Rhodobacteraceae’, sharing the highest 16S rRNA gene sequence similarity with Limibaculum halophilum CAU 1123^T (96.8%). The major menaquinone Q-10 and the dominant unsaturated fatty acid (C_18:1ω7) in this family were also detected in the strain M0105^T. The genome sequence possesses a circular 4.1 Mb chromosome with a G + C content of 67.9%. Strain M0105^T encoded many genes for cellular stress resistance and nutrient utilization, which could improve its adaptive capacity to the mangrove environment. Values of conserved proteins (POCP), average nucleotide identity, average amino acid identity (AAI) and DNA–DNA hybridization (dDDH) between the isolate and closely related species were below the proposed threshold for species discrimination. Information from phenotypic, chemotaxonomic and phylogenetic analyses proposed that strain M0105^T should be assigned to a novel genus within the family ‘Rhodobacteraceae’. Thus, we suggested that the strain M0105^T represents a novel species in a new genus, for which the name Thermohalobaculum xanthum gen. nov., sp. nov. is proposed. The type strain of the type species is M0105^T (= BGMRC 2019^T = KCTC 52118^T = MCCC 1K03767^T = NBRC 112057^T).