Evidence for oscillation in monolithic molecular single crystals of a thiophene/ phenylene co-oligomer is reported. The laser oscillations (see Figure) are characterized by naturally formed crystal facet cavities with molecular-scale flatness. The multimode laser oscillation in a Fabry-Perot resonator is characterized by sharply resolved spectroscopic lines with their full width at half maximum down to only 38 pm. The laser oscillation is characterized by the presence of a well-defined threshold.