A bacterial strain, designated an-8(T), was isolated from a freshwater shrimp culture pond in Taiwan and characterized using a polyphasic taxonomic approach. Cells of strain an-8(T) were Gram-reaction-negative, aerobic, rod-shaped and non-motile, formed yellow-pigmented colonies and grew at 15-30 �XC (optimum 25 �XC), pH 7-8 (optimum pH 8.0) and in 0-1 % (w/v) NaCl (optimum 0 %). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain an-8(T) belonged to the genus Flavobacterium and its most closely related neighbours were Flavobacterium terrigena DS-20(T) and Flavobacterium terrae R2A1-13(T) with sequence similarities of 95.1 and 94.9 %, respectively. Strain an-8(T) contained iso-C(15 : 0), summed feature 3 (C(16 : 1)�s6c and/or C(16 : 1)�s7c), iso-C(16 : 0) 3-OH, iso-C(15 : 0) 3-OH, iso-C(17 : 0) 3-OH and iso-C(15 : 1) as the major fatty acids. The major isoprenoid quinone was MK-6. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidyldimethylethanolamine, phosphatidylserine and several unidentified polar lipids. The G+C content of the genomic DNA was 39.8 mol%. On the basis of the phylogenetic and phenotypic data, strain an-8(T) represents a novel species of the genus Flavobacterium, for which the name Flavobacterium macrobrachii sp. nov. is proposed. The type strain is an-8(T) (= BCRC 17965(T) = LMG 25203(T)).