Jansen’s wrasse (Thalassoma jansenii) is a species of ray-finned fish, a wrasse from the family Labridae which is native to the Indian Ocean and Pacific Ocean. In the south-western Pacific Ocean it is replaced by sibling species black-barred wrasse (Thalaaoma nigrofasciatum). In its initial phase Jansen’s wrasse is white with three black bars, the first of which is on upper half of head and anterior body and contains a yellow strip on the margin of the gill cover. The second band goes across dorsal fin and ends at the anus while the third covers most of the body and the rear parts of dorsal and anal fins. The terminal phase males have yellow between black bars. The pectoral fins have a bluish colour. This species can grow to 20 cm (7.9 in) in total length. It has 8 spines and 13 soft rays in its dorsal fin and 3 spines and 11 soft rays in its anal fin.
