A Gram-negative, heterotrophic, aerobic, marine bacterium, designated AIT1(T), was isolated from a seawater sample collected in the shallow coastal region of Bitou Harbour, New Taipei City, Taiwan. Cells grown in broth cultures were straight or slightly curved rods that were motile by means of a single polar flagellum. Strain AIT1(T) required NaCl for growth, grew optimally at 30-40�XC and with 1.5-5.0% NaCl, and was incapable of anaerobic growth by fermentation of glucose or other carbohydrates. The isoprenoid quinones consisted of Q-8 (95.2%) and Q-9 (4.8%). The major polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The cellular fatty acids were predominantly iso-branched and included iso-C(17:0) (26.5%), summed feature 9 (comprising iso-C(17:1)�s9c and/or 10-methyl C(16:0); 25.9%) and iso-C(15:0) (20.5%). The DNA G+C content was 51.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AIT1(T) formed a distinct lineage within the class Gammaproteobacteria and was most closely related to members of the genus Idiomarina in the family Idiomarinaceae (91.5-93.9% 16S rRNA gene sequence similarity). The phylogenetic data, together with chemotaxonomic, physiological and morphological data, revealed that the isolate should be classified as a representative of a novel species in a new genus in the family Idiomarinaceae, for which the name Aliidiomarina taiwanensis gen. nov., sp. nov. is proposed. The type strain is AIT1(T) (=JCM 16052(T)=BCRC 80035(T)=NCCB 100321(T)).