We describe Furcifer timoni sp. nov., a new colourful and morphologically highly distinct chameleon from Montagne d’Ambre National Park in northern Madagascar. Males of this rainforest species are characterized by short paired bony rostral appendages which are completely absent in females. The new species differs from all other Furcifer species except F. bifidus (Brongniart, 1800) and F. balteatus (Duméril & Bibron, 1851) by a light ventrolateral band that is composed of scales which are arranged in a rosette-like manner. It differs from F. bifidus and from F. balteatus by smaller size, shorter rostral appendages of the males, and colouration. We suspect that F. timoni may be a cryptic species of the forest canopy. Furthermore, we designate a lectotype for Dicranosaura bifurca var. crassicornis Gray, 1864 and confirm its synonymy with Furcifer bifidus.