Jacobulus is an extinct genus of prehistoric ray-finned fish that lived during the Early Triassic epoch in what is now northern Madagascar 252.3 to 251.3 million years ago. The type species is Jacobulus novus (monotypy). It was a small fish less than 10 cm in length. J. novus ecology was a grazer-detritivore. It belongs to the Parasemionotidae together with Albertonia, Candelarialepis, Icarealcyon, Lehmanotus, Parasemionotus, Qingshania, Stensioenotus, Suius, Thomasinotus, and Watsonulus.