This paper reports on the first record of the Pacific oyster, Crassostrea gigas (Thunberg, 1793), in the southern Black Sea, based on a sample of 235 specimens collected from rocky shores 23 km west of the city of Ordu, northern Turkey. Species identification was confirmed by nucleotide sequencing of two mitochondrial gene fragments, viz. COI and 16S rRNA in five individual oysters. Analyses of mitochondrial cytochrome oxidase I (COI) sequences from southern Black Sea coastlines suggest that all samples were Pacific oyster, Crassostrea gigas. In addition, this study provides the first analysis of length-weight relationships (LWR) for C. gigas collected from the southern Black Sea. The relationship between mean shell length (SL) and mean total weight (W) was SL = 0.0143W(1.6662) (r(2) = 0.6589). The specimens were morphometrically characterized as follows: mean shell length (SL) 59.57 +/- 13.65 mm (range: 24.09-98.17 mm), mean shell width (SWi) 28.05 +/- 6.91 mm (range: 10.50-50.87 mm), mean total weight (W), 13.62 +/- 5.03 g (range: 0.78-36.89 g), and mean meat weight of 1.5 +/- 0.90 g (range: 0.01-5.83 g). The relationships between the morphometric parameters suggested negative allometric growth. According to the results, C. gigas has created breeding populations on the Turkish Coasts, becoming the dominant species on some hard substrate, including rocky bottoms and large rocks used as fill locally to gain more land in the coastal area.