Saprolegnia brachydanis is described from zebra fish (Brachydanio rerio) in Wuhan, Hubei Province, China. The species is illustrated and compared with other species of the genus. The distinctive characteristics of S. brachydanis are the production of glomerulate oogonia wrapped around by predominantly monoclinous antheridia which can be up to eight in one oogonium. The oogonial stalks are short, straight, or curved and the antheridia, twisted, can enwind one or more oogonia. The oospores cannot mature or easily abort. Morphological features of the oomycete and the ITS sequence of its rDNA as well as the comparison with related species are discussed in this article.