In this letter, a novel scheme to generate optical frequency combs (OFCs) using gain switched (GS) semiconductor nanolasers (SNLs) is proposed. Numerical calculations have been performed using rate equations, which include the Purcell cavity-enhanced spontaneous emission factor F and the spontaneous emission coupling factor β . The results demonstrate that broadband OFCs (10 dB frequency span, f10>1THz ) can be generated over a wide range of parameter space due to the intrinsic dynamics of the SNLs. Moreover, it is observed that f10 is associated with the effective reduction of the carrier lifetime and increases with increase of the bias current. The broadband OFCs generated in GS SNLs offers opportunities for their practical applications and notably in photonic integrated circuits.