A Gram-stain-negative, rod-shaped, aerobic bacterial strain designated LLYu02^T was isolated from intertidal seawater of the South China Sea. Strain LLYu02^T exhibited growth at 10–37°C (optimum 37°C), pH 6–9 (optimum pH 6–7), and 0–10% (w/v) NaCl (optimum 1%). Phylogenetic analysis based on 16S rRNA gene sequences revealed that CXY002^T shares 96.65%, 96.59%, 96.51%, and 96.51% sequence similarities with Arenibacterium halophilum CAU 1492^T, Phaeobacter  gallaeciensis DSM 26640^T, Leisingera daeponensis DSM 23529^T, and Phaeobacter piscinae 27-4^T, respectively. Phylogenomic reconstruction further shows it's likely a new genus. Digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between LLYu02^T and closely related species ranged from 19.7% to 24.4% and 77.91% to 81.82%, respectively, both below the recommended thresholds for species demarcation (70% for dDDH and 95–96% for ANI). The genomic DNA G+C content was determined to be 36.5 mol%. The predominant respiratory quinone was menaquinone-10 (MK-10), while the major fatty acids comprised summed feature 8 (C_18:1 ω7c). Polar lipids included phosphatidyl choline (PC) phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and six unidentified lipids (L1–L6). Genome annotation confirmed the full alkane degradation pathway. Based on polyphasic taxonomic evidence encompassing phenotypic, chemotaxonomic, and genomic characteristics, strain LLYu02^T represents a novel species within the genus Arenibacterium, for which the name Arenibacterium halophilum sp. nov. is proposed. The type strain is LLYu02^T (MCCC 1K09932^T = ).