K3C60 has been quantum-confined inside the pores of mesoporous niobium oxide. Examination of the electronic properties of this new family of 1D potassium (shown in pink in the Figure) fullerides shows that, contrary to previous experimental data on bulk K3C60 (but consistent with theoretical calculations), these nanowires are insulating at room temperature and do not undergo a superconducting transition at liquid-helium temperature.