The authors report achieving ultrahigh electron mobilities in excess of 200,000 cm²V⁻¹s⁻¹ at electron densities of approximately 2×10¹¹ cm⁻² by suspending single-layer graphene. The suspension is achieved by placing the graphene approximately 150 nm above a Si/SiO₂ gate electrode, using a combination of electron beam lithography and etching. In situ cleaning of the graphene by current-induced heating significantly improves electrical transport. The Dirac peak widths are reduced by a factor of 10 compared to traditional, non-suspended devices, indicating a significant improvement in sample quality. The study demonstrates that extrinsic scattering, primarily from the substrate, is a major barrier to high mobilities in graphene devices, and that removing the substrate can lead to substantial mobility enhancement. The authors also observe that current annealing further improves mobility and reduces charge inhomogeneity, suggesting that impurities trapped between the SiO₂ and graphene layers are responsible for the observed limitations.The authors report achieving ultrahigh electron mobilities in excess of 200,000 cm²V⁻¹s⁻¹ at electron densities of approximately 2×10¹¹ cm⁻² by suspending single-layer graphene. The suspension is achieved by placing the graphene approximately 150 nm above a Si/SiO₂ gate electrode, using a combination of electron beam lithography and etching. In situ cleaning of the graphene by current-induced heating significantly improves electrical transport. The Dirac peak widths are reduced by a factor of 10 compared to traditional, non-suspended devices, indicating a significant improvement in sample quality. The study demonstrates that extrinsic scattering, primarily from the substrate, is a major barrier to high mobilities in graphene devices, and that removing the substrate can lead to substantial mobility enhancement. The authors also observe that current annealing further improves mobility and reduces charge inhomogeneity, suggesting that impurities trapped between the SiO₂ and graphene layers are responsible for the observed limitations.