Bedotia masoala, a new species of Malagasy rainbowfish, is described from the Ankavanana drainage on the eastern slope of the Masoala Peninsula, northeastern Madagascar. The new species is readily distinguished from congeners by a unique blotchy, mottled, or barred lateral pigmentation pattern, and further distinguished from Bedotia marojejy, the only additional Bedotia that lacks a prominent, solid, dark midlateral stripe, by a higher vertebral count, a greater number of scales in lateral series on the flanks, and by the presence of palatine and well–developed endopterygoid tooth patches. Bedotia masoala is endemic to the Ankavanana drainage, an eastward flowing basin of the Masoala Peninsula.