We here report naphtho[2,1-b:6,5-b']difuran derivatives as new p-type semiconductors that achieve hole mobilities of up to 3.6 cm(2) V-1 s(-1) along with high I-on/I-off ratios in solution-processed single-crystal organic field-effect transistors. These features originate from the dense crystal packing and the resulting large intermolecular pi-orbital overlap as well as from the small reorganization energy, all of which originate from the small radius of an oxygen atom.