A new species of bumblebee goby, Brachygobius jennie sp. nov. (Teleostei, Oxudercidae), is described based on 31 specimens collected from the Hengqin Island, Guangdong Province, China. This new species is distinguished from all other valid species of Brachygobius by its extreme small size (SL < 9 mm) and distinctive number, position, size and shape of its black bars. It possesses four complete (forming ring) or nearly complete post-cephalic, relatively narrow bars, two of which are located posterior to the base of the anal fin. The first bar behind the head extends pigmentation to the first dorsal fin but does not reach the midventral line. The second bar, chevron-shaped and located below the second dorsal fin, extends pigmentation onto that fin and ventrally reaches the midventral line and the anal fin. Cytochrome oxidase subunit I-based analyses, including six out of the eight valid species of Brachygobius, show Brachygobius jennie sp. nov. to be more than 10% genetically divergent from other species, supporting the morphological diagnosis and confirming its distinct taxonomic status. With a maximum size of less than 9 mm SL (based on observations of 106 specimens), the new species is not only the smallest species of Brachygobius, but also one of the smallest known gobioid fishes.